What muscle supports the medial knee?

X-Ray of a KneePick one of the following answers:

a) tibialis posterior
b) tibialis anterior
c) adductor magnus
d) gracilis
e) quadriceps

The adductors are a group of 5 different muscles along the inside of the thigh.  They are:

  • pectineus
  • adductor brevis
  • adductor longus
  • adductor magnus
  • gracilis

They all adduct (pull the limb towards the midline) the lower limb, but only one of them crosses and supports the medial knee.  That is d) the gracilis.  This muscle is the only muscle that supports the medial knee.

If this muscle is weak, the knee will want to deviate towards the midline in a way that would cause a knock-kneed deformity.  This motion is initially prevented from happening because of the relatively strong medial collateral ligament.  If the gracilis remains weak for a long enough period of time, the increased tendency for the knee to want to deviate medially will gradually stretch the ligament.  Then the knock kneed deformity will manifest.

Gracilis - BP3D
The stretched ligament will now result in sloppy movement of the knee and allow the bones to ride onto tissues that they normally do not.  This will eventually result in additional damage to tissues such as the joint capsule, the minisci and the other 3 ligaments of the knee.  If this process is not stopped and corrected, the tissue damage will tend to keep spreading throughout the joint in a process known as joint degeneration.

If the process has not progressed too far, it typically can be stopped and reversed.  Correcting the progression can involve many different diagnostic and therapeutic procedures. Commonly, testing the muscles of the knee as well as the muscles supporting the joints above and below the knee for imbalances will be part of the diagnostic process. One of the therapies will then typically be giving exercises for the weak muscles and some type of relaxing technique to muscles which are overly strong.

The Diagnosis Foundation has courses available for the physicians, trainers, therapists and others to learn how to test individual muscles for strength.  Contact: Info@DxFoundation.org

Weak Gluteus Max: Tibial Head leads to….

Gluteus max - 1.4 - BP3DIf your Gluteus maximus: Tibial Head (GM:TH) is weak, what kinds of performance and health issues can you get?  It’s a significant factor for iliotibial band syndrome, hip bursitis, fall prevention for seniors, lateral knee protection, hip arthritis prevention, contributes to pelvic tilt control and lots more.  Let’s look at GM:TH anatomy, actions, measurement methods along with the implications weak GM:TH strength can have on your athletic performance and health.


The Gluteus Maximus (GM) is the largest muscle in the human body and makes the largest contribution towards shaping the buttocks.  It originates along the posterior (back) and lateral portion of the ilium of the pelvis between the iliac crest and the posterior gluteal line.  It spits into two portions that insert into two separate areas.  The deeper portion of the muscle inserts into the gluteal tuberosity of the femur.  The other portion of the gluteus maximus which this post will be dealing with, inserts into the broad and flat iliotibial band.  From there, the iliotibial band runs down the lateral (outside) of the thigh, crosses the knee and inserts into the lateral tibia, just below the large knobby tibial condyle.

Note: The two components of the GM divide into two distinctly different insertions and have significantly different functions as well as clinical implications.  I will be identifying each component of the muscle with different names (GM Femoral Head & GM Tibial Head) even though this nomenclature distinction is not commonly found in the literature.


The main action of this muscle will be to cause a compound movement of the lower limb.  It will result in the thigh:

  • extending
  • abducting
  • externally rotating

TFL - 1.4 - BP3DTFL - Glut Max - Iliotibial band - Y





The other muscle to attach into the iliotibial band is the tensor fascia latae (TFL) resulting in a ‘Y’ shape.  The GM:TH forms one arm of the Y while the tensor fascia latae forms the other arm of the Y.  The iliotibial band forms the leg of the Y.  If both the GM:TH and the TFL work simultaneously, the GM:TH actions of extension and external rotation of the thigh will be cancelled out by the opposite actions of the TFL, resulting in straight abduction of the thigh.


Gluteus medius - 1.4 - BP3DWeakness in the GM:TH can be determined with manual muscle strength testing, careful observation of movement during walking, climbing, bending, thigh abduction and other tests. Supporting information can be gained through a careful history as well as physical examination for neurological, vascular and orthopedic signs.  Detailed measurement of GM:TH muscle strength are available with specialized equipment such as tensiometers and isokinetic dynamometers when required for insurance purposes, research or in advanced cases.

Performance Issues

Athletic performance issues related to weakness of this muscle will be dependent on if it is working alone or in a joint effort with another muscle.  When working alone, the action will be a compound extension, abduction and external rotation of the thigh.  When working with one or more other muscles, you can obtain any of these three motions alone.

Compound Thigh: Extension/Abduction/External Rotation – The GM:TH will accelerate the thigh in a diagonal direction from the front inside to the back outside while externally rotating the thigh.  This muscle will also decelerate the opposite motion (i.e. when you are doing a forward diagonal kick to the inside, the GM:TH will slow down the thigh at the end of your intended motion.)

Ballet Dancer Mid-air in JumpThe classic athletic motion using this muscle would be the martial arts backward diagonal kick.  Any activity that include running or jumping forward on the diagonal to the opposite side will use this muscle extensively.  Less commonly, climbing hillsides, roofs or bleachers on a diagonal will utilize this muscle.

Thigh Abduction – When used in conjunction with the TFL, the GM:TH will accelerate the thigh into straight aBduction (lifting the leg to the side).  This combination of muscles will also be used to decelerate the thigh at the completion of doing aDduction.

Common athletic motions utilizing this action would include: straight sideways shuffle motions, side soccer kicks or straddle jumps as well as decelerating the swing through phase of side crossover motions.

Thigh Extension – When used in conjunction with the GM: femoral head or hamstrings, extension of the thigh will result.  This combination of muscles will also decelerate thigh flexion.  When the thigh is relatively stable (i.e. when standing or sitting), this muscle will also rotate the pelvis posteriorly to help flatten the low back.

Running Back Carrying BallThis motion is used extensively in almost any activity that involves forward propulsion – running, bicycling, climbing or jumping.  It is also used when the trunk is rising from a flexed position (picking something off the floor or jumping from a coiled position).

Since there are other substantial muscles involved in these motions, weakness of the GM:TH may not be immediately apparent  Careful assessment of each of these components can give vital clues to which of these muscles is the weak link that would give you the best returns from focused exercise attention.

Thigh External Rotation – The GM:TH will work with the posterior fibers of the gluteus medius and a few other small muscles in the pelvis to accelerate external rotation of the thigh. This combination will also rotate the trunk in the opposite direction.  This combination of muscles will also decelerate the opposite motion.  i.e. The GM:TH will decelerate internal rotation at the end of your intended movement.

Athletic motions utilizing this motion would include: the common activity of turning the leg outward in preparation for a change of direction when the limb is non-weight-bearing during walking or running.  This muscle group would also be involved in turning the trunk in the opposite direction to alter course when weight bearing.  Many agility maneuvers will utilize this action which could be easily applied during obstacle course runs, avoiding tackles in football changes in direction for soccer, volleyball, basketball, etc.

Clinical Issues – Acute & Chronic

Injury & Disease Susceptibility – In addition to performance degradation, athletes with weak GM:TH will be susceptible to increased rates of injury due to knee and hip imbalance and instability.  Should these imbalances be of sufficient severity or persist for a long enough period of time, diseases from biomechanical complications can result.

X-Ray of a KneeLateral Knee Support – The GM:TH via the iliotibial band is the only active support for the lateral knee.  Weak support for the lateral knee will allow for increased strain on the lateral collateral ligament, one of the four main ligaments of the knee.  Should this ligament become lax, the knee will have excess play, abnormal movements and susceptibility to meniscus damage.  Should the menisci become damaged, complete recovery of the knee becomes much less likely and continued degeneration of the knee becomes more likely ultimately culminating in osteoarthritis

Iliotibial band Syndrome – This syndrome is the result of excess friction, irritation and damage on the distal band that is very common among distance runners.  Among people who run the same number of miles on a weekly basis, only a percentage of people will get this syndrome indicating that additional factors are involved besides distances run.

One factor which make a person more prone to developing this syndrome is and imbalance of the muscles controlling the knee or the iliotibial band.  With increased imbalances of the knee, the joint will not remain centered properly putting excess strain in one or more directions.  Imbalances also can lead to excess motion of the knee-joint with each step, increasing the amount of friction and damage on the band.

Crutches shadow personHip bursitis – The hip has a number of different bursa’s around the joint.  Similar to iliotibial band syndrome, should the muscles around the hip become imbalanced, excess strain or motion will place increased friction on the bursa’s, increasing their rate of injury.  Should the damage to the bursa’s happen faster than the tissues be repaired, inflammation and eventual failure result.

For example, people, with a weak GM:TH, will experience an increased amount of dip in their pelvis on the unsupported side during the one-legged stance phase of walking.  This results in the bursa overlying the hip bone to experience double, triple or more increased rates of rubbing and friction than when all the muscles supporting one-legged stance are strong.

Seniors dancingFall prevention for seniors – The ability to maintain balance is dependent on many factors.  One of them is having adequate strength to adapt to the environment fast enough to prevent falling.  The greater the strength and balance of all of the postural muscles the better the capability will be to adapt to an unexpected rock underfoot or the running child without falling.

Hip replacement - NIH - Public domain



Hip arthritis prevention – If the muscles which control the hip-joint become imbalanced, the femoral head, the ball which sits within the hip socket, will put increased pressure on one side or another.  The increased pressure will put an accelerated degree of tissue turnover on the joint surface.  The greater the degree of muscle imbalance, the more pressure imbalance will be on the articular surfaces and the greater the rate of tissue damage will be. Should this persist for a long enough period of time, the cartilage will be worn away and direct bone on bone contact will happen.  This eventually leads to bone erosion, arthritic proliferation and joint degeneration.

Pelvic tilt control – The GM:TH is one of the major muscles controlling the degree of pelvic tilt.  Weakness of this muscle will contribute to a pelvis with an increased tilt forward which will have ramifications up the kinetic chain.  This will contribute to causing an increased curve forward in the low back (or hyperlordosis).  This increased arch in the low back will put the low back muscles at a mechanical disadvantage, increasing their likelihood of receiving damage or a lumbar strain.

The key step for learning if you or your family have a weakness of the GM:TH is getting it tested.  You can also learn how to do manual muscle strength testing through  seminars  and online through the DxF.

Weak Tibialis Anterior leads to…

Tibialis anterior - 1.4 - BP3DIf your Tibialis Anterior (TA) is weak, what kinds of performance and health issues can you get?  It’s a significant factor for foot pronation, plantar fasciitis, achilles tendonitis, shin splints, anterior compartment syndrome, knee pains and lots more.  Let’s look at TA anatomy, actions, measurement methods along with the implications weak TA strength can have on your athletic performance and health.

Anatomy – The TA muscle is located in the front of your lower leg region.  The top of the muscle attaches to the upper 2/3rd of the lateral (outside) tibia.  The muscle runs down the front of the shins, connects to its’ long tendon which runs in front of the instep.  From there, the tendon continues towards the medial side of the foot, attaching around the mid foot at about the peak of the long foot arch into the 1st cuneiform and the base of the 1st metatarsal bones.

Action – The main action of this muscle will be to dorsiflex your foot (pull your foot up) and twist the sole of your foot to face inward (inversion).  The quick way to refer to this motion is that it twists your foot up & in.  This is one of the key ‘stabilizing’ muscles of the foot.  In addition to twisting your foot up and in, the TA is also one of the primary muscles holding up the long arch of the foot.

Tib Ant - Sup view - half bodyDiagnosis – Weakness in the TA can be determined with manual muscle strength testing, careful observation of ankle movement during walking, running and at rest, long arch height measurements and other tests. Supporting information can be gained through a careful history as well as physical examination for neurological, vascular and orthopedic signs.  Detailed measurement of TA ranges of motion and muscle strength are available with specialized equipment such as tensiometers and isokinetic dynamometers when required for insurance purposes, research or in advanced cases.

Functional Implications – When the TA muscle is weak, you will not have the strength you should when a) moving the forefoot up & in, b) your ankle will be unstable and c) there will be some degree of difficulty holding up your long arch (excessive foot pronation) when the foot is put under more stress than the muscle can handle.  In more advanced weaknesses, the foot will be unable to hold the long arch up during even mild stress such as weight-bearing.  With extreme or prolonged weakness, the long arch may become permanently deformed to the flat position (flat-footed) even without weight-bearing.

Performance Issues (Arch) – Difficulty in holding up the long arch will have implications in a very large number of sports.  Any athlete involved in sports which include running will suffer to some degree.  If the long foot arch is fully collapsed, shock absorption will be reduced (depending on what type of foot strike you use).

Performance Issues (Knee) – When the ankle pronates, the long arch collapses medially.  If you stand and look at your knee while you pronate your foot, you will see that this motion also results in the knee deviating medially (towards ‘knock kneed’). This stretches the medial collateral ligament and strains one of the thigh adductor muscles (the gracilis).

Athletes in sports that require high power outputs in the legs (such as weight lifting and high jumping), with weak TAs, may notice that their knees ‘give out’ or ‘buckle’ medially when under high stress.  When joints buckle outside of their normal ranges of movement, reflexes are initiated which severely restrict continued muscle contraction.  A weak TA can effectively become the weak link which limits your athletic performance.

Soccer kickAthletic Performance Issues (Up & In) – Sports that use the motion of twisting the foot up and in will suffer when this muscle is weak.  Kicking a football or soccer ball in a forward / diagonal direction is a clear example.  While the main power behind the kicking is due to the larger thigh muscles, additional power is also derived from the TA to give you the extra power needed to advance you to the next level of athletic performance.  Perhaps more important than the extra power, will be the degree of ball control that is lost in kicking because the forefoot cannot maintain a reliably stable kicking surface.

Sports that require agility and rapid lifting of the foot like basketball, volleyball and dance will also suffer.  Athletes who need agility with strong lateral movement will be aided by the TA to evade their competitors as in football.

Injury Susceptibility – In addition to performance degradation, athletes with weak TAs will be susceptible to increased rates of injury due to ankle and knee instability.  Medial to lateral movement of the foot may be increased as the foot over pronates with each step.  This will result in a few complications, including:

  • Stretching the medial ankle ligaments that help maintain joint integrity against ankle sprains
  • The achilles tendon will experience excessive movement at the ankle joint leading to potential achilles tendonitis
  • The knee deviates medially each time the foot pronates.  This leads to stretching of the medial collateral ligament of the knee, knee instability and a wide range of secondary issues such as potential for cartilage damage.

Chronic & Severe Weakness – People who experience weak TA issues for many years are putting their feet and knees through excessive wear and tear that can eventually lead to cartilage damage, osteoarthritis and potential for surgery.  Advanced weakness of ankle stabilizers can contribute to susceptibility to falls for seniors.

Extreme weakness of the TA can contribute to ‘foot drop’ or difficulty lifting the foot up, dragging the toes, an unusual gait and increased tripping.  There are other muscles in the foot that contribute to holding the foot up, so typically this will not happen unless there is severe weakness of all of these muscles, which more typically happens when there is nerve damage.

Learn manual muscle strength testing through seminars and online through the DxF.

Regarding “a pulled groin”, is the groin a….

Thigh front - WC public domaina) muscle
b) bone
c) region
d) tendon
e) cartilage

The expression of having a ‘pulled groin’ seems to imply that it is a specific muscle getting damaged.  This would not be true because the groin is actually, c) a region.  It is the triangle formed in each upper thigh by the crease between the torso and the thigh superiorly, the symphysis pubis in the midline and femur forming the lateral boundary.  Muscles located in the groin region include:  the upper portions of all 5 adductor muscles as well as the distal portion of the iliacus and psoas major muscles.

Someone who gets a ‘pulled groin could have received an injury to any of 7 different muscles.  It is important to differentiate which muscle is involved in order to:

  • help understand why a pulled groin developed (i.e. was in wholly or partially due to an imbalance of the muscles in the groin region?)
  • rehabilitate the injured muscle fully with direct exercises at the proper time
  • prevent future injuries by correcting imbalances before they become symptomatic

“Pulled groins take a long time to heal!”

I grew up hearing that expression many times.  Why is that?  Is it true?  There doesn’t appear to be a basis for muscle strains in the groin region to take any longer to heal than any other muscle pull.  All the muscles in the groin are crossing the hip-joint which is particularly stable, so it doesn’t seem that there would be unusual mechanical stresses on muscles in the region. Pulled muscles in general, can be as minor as those that give symptoms lasting a few minutes, to complete ruptures, and anywhere in between.  So why is there an impression that groin pulls last a long time?

If groin strains do last longer than other muscle pulls, perhaps one factor is because of the relative lack of attention given to differentiating which muscle is injured in this region during discussions, diagnosis and treatment.  Let us consider for a moment.  Why is it that the adductors and abductors of the thigh are almost always referred to as a group rather than the individual muscles within the group?  If you have studied anatomy and know the different muscle names in the groin region, how would you test to find out which muscles are too strong or too weak?  If you work in the health or fitness industries and have determined which muscles in the groin region need exercise attention, how would you exercise each of them separately or target one specifically?

When to Use: Broad Based Exercises vs. Targeted Exercises

When muscles around a joint are balanced, then broad based exercises that work all the muscles around a joint are more likely to be appropriate.  When one muscle around a joint is significantly weaker than its’ neighbors, it is more likely that a targeted approach may be get you better results.  The first step to knowing if broad based or targeted exercises will be more appropriate, is assessing how strong each individual muscle is.

Start learning how to differentiate which muscles are weak and strong by taking the DxF course on Muscle Imbalance Testing.  Available by online courses with certification or without and by seminars at our location or at yours.

How many adductor muscles are there?

Magnifying glass child - MSThere are lots of muscles that are ‘adductors’.  Literally, this only refers to muscles which bring a limb closer to the midline.  In common usage however, ‘adductors’ are used to refer to a group of muscles that perform this function on the inner thigh.

This group of muscles is made up of 5 different muscles.  They are (from the shortest to longest):


  • Pectineus
  • Adductor brevis
  • Adductor longus
  • Adductor magnus &
  • Gracilis

Each of these muscles performs adduction, but they differ from each other in what part of the thigh range of motion they adduct best as well as what other motions they each contribute to.

Some of the adductors for example contribute significantly to thigh rotation (pectineus), some to centering the femur within the hip socket in order to minimize wear and tear.  Only one of the five (the gracilis) crosses the knee joint as well, contributing to adducting the lower leg.  They all have a role to play in helping you maintain your balance and preventing falls.

Learn more about the actions of muscles in your legs, how to test for and determine if they are imbalanced.   See the DxF courses on Muscle Imbalance Testing, available online, at our seminars or through a seminar scheduled to take place at your facility.

Weak pectineus muscle leads to…

Pectineus - 1.4 - BP3D

When the pectineus muscle is weak, what kinds of performance and health issues can you get?  Let’s look at the frequency of Pectineus Muscle (PM) weakness, its anatomy, actions, measurement methods along with the implications weak PM strength can have on your athletic performance and health.

Frequency of Weakness

The Diagnosis Foundation has been including this muscle test in our current screening program on Muscle Imbalances, and it is one of the most frequent weakness we have been finding.  It is weak in close to 80% of the athletes we have been testing.  (You can imagine how frequently it will be involved when we include non-athletes in our screening program).  Keep in mind, this is not a statistically valid way of determining frequency, so real population numbers could be dramatically different.


The PM is located on the medial side (inner side) of the upper thigh and is moderately deep lying underneath the psoas major muscle and superficial to the adductor brevis.  The superior (top) end of the muscle attaches to the superior ramus (upper arm) of the pubic bone of the pelvis.  The muscle runs through the groin area and connects to its’ very short tendon just before it attaches to the femur (thigh bone) just below the lesser trochanter.

 The pectineus is shortest of the 5 adductor muscles which pull the thigh inward  They are (from the shortest to longest): pectineus; adductor brevis; adductor longus; adductor magnus &; gracilis.

The PM is one of the muscles in the groin region, the triangle formed in each upper thigh by the crease between the torso and the thigh superiorly, the symphysis pubis in the midline and femur forming the lateral boundary.  Other muscles in the groin region include the other 4 adductors as well as the distal portion of the iliacus and psoas major muscles.  This being mentioned as any of these muscles can be involved with a ‘pulled groin’.


The main action of this muscle is to pull the thigh inward.  It is most effective compared to the other adductors in performing a full ‘crossover’. For example, if you do a side step and cross one leg either in front of or behind the other limb, the PM is the prime mover crossing the leg over the other.

The PM is least effective compared to the other adductor muscles when the limb is fully abducted (pulled away from the midline).  This ineffective motion would be exemplified when you initiate pulling your legs together starting from the fully straddle split position.

The PM also give some significant contribution to externally rotating the thigh and a very slight contribution to flexing the thigh.

Muscle Weakness Diagnosis

Pectineus - anterior view - legs onlyWeakness in the PM can be determined with manual muscle strength testing, careful observation of hip alignment during walking, running and at rest as well as other tests. Supporting information can be gained through a detailed history and physical examination for neurological, vascular and orthopedic signs.  Measurement of PM ranges of motion and muscle strength are available with specialized equipment such as tensiometers or isokinetic testing devices when required for more detailed examinations, insurance purposes or research.

Functional Implications

When the PM muscle is weak, you will not have the performance capabilities you should have in the following situations. 1) Leg crossovers; 2) External rotation of the thigh &: 3) Hip stabilization.

Adductors Effectiveness1) Leg Crossovers – The PM is involved in adduction of the thigh along with 4 other muscles.  The 5 adductors have varying degrees of adduction efficiency across the entire possible range of motion.  This is the result of the muscle length and is’ points of attachment.  Each muscle contributes a percentage of its’ force into adduction and another percentage into vertical movement.  

In general, as we move the thigh from the fully abducted starting position towards a full crossover, the longest adductors have the best adduction to superior displacement ratios. (i.e. they are most efficient for adduction)  As your limb move towards full crossover, the shorter adductors have the better adduction:superior displacement ratios.  This can be summarized by the graph above which shows where each adductor muscle is the most efficient across the full range of adduction motion.

Snow skiier - MSAs a result of this, people with a weakness of the PM will have poor strength and control when in the extreme crossover position.  This will also manifest with issues in any activity that uses the hips in angulation.  Think of the uphill leg of the downhill skier going around a mogul.  Soccer players doing crossover kicks medially will use the PM extensively.  Activities on sloped surfaces will also use the PM extensively (Think of roofers traversing a roof.)

Hip Socket - Force Balance 2) External rotation of the thigh – The origin and insertion of the PM has the greatest anterior to posterior angulation of the adductors.  I.e. it has the most fibers capable of rotating the thigh externally of all the adductors.  This motion is also assisted by 2 muscles on the opposite side of the thigh (the gluteus maximus (glut max) and some of the fibers of the gluteus medius (glut med)).

External thigh rotating maneuvers are used with pivots and changes in direction.  Sharp turn with great changes in direction require more force capability to change the momentum of the body mass compared to minor corrections.  Agility and the ability to outmaneuver opponents will be the end results of strong external rotation in competitive sports.  Versatility in artistic expression will be enhanced in dance, gymnastics and other solo athletic events.

3) Hip stability – The PM will stabilize the hip joint in the adduction / abduction plane, particularly when in the crossover position.  It will accelerate adduction in this position as well as serving as the antagonist or ‘braking’ function for abduction.  The PM will also participate in hip stabilization in the transverse plane during rotation of the thigh.  It will accelerate external rotation as well as being the antagonist that applies the ‘brakes’ for internal rotation.

Seniors dancingWhen in the early stages of instability, PM weakness will manifest in a decrease in athletic performance.  As the imbalance continues, there will be an increased susceptibility for falls.  Should the weakness or imbalance become severe enough or last long enough, there will be an increased chance of injuries or health issues.

Injury Susceptibility

People with chronic  or more pronounced weakness of the PM, imbalanced strength at the hip joint, will be more susceptible to 1) groin strains; 2) hip degeneration.

1)  Groin strains – When the PM is weak compared to the other muscles crossing the hip joint, there will be opportunities for the stronger muscles to overpower the PM, causing damage.  The PM can also be damaged from doing repeated activities at the limits of what the strong muscles can tolerate yet do not typically involve the PM.  A variation in this procedure (i.e. a slight slip part way through a maneuver) can redistribute force onto the relatively incapable PM.  Not only will the weak PM be unable to recover from the slip appropriately, it will also be more vulnerable to muscular damage.

Hip replacement - NIH - Public domain2) Hip degeneration – When the externally rotating muscles on the inside (PM) & outside (glut. max. & med.) work in concert, not only do you have more strength with this maneuver, you also are able to keep pressure within the hip socket more centered.  This reduces the wear and tear on the cartilage of both the ball and socket of the hip joint.  Should an imbalance of the muscles crossing the hip joint persist for a long enough period of time, the additional pressures on the ball and socket will first erode the articular cartilage at an accelerated rate., Eventually, the increased pressures will break through the cartilage, resulting in direct bone on bone contact.  Should this hip be exposed to direct bone on bone contact for a sufficient period of time, bone spurs and erosion will develop and eventually, joint failure leading to a need for hip replacement.

Knowledge to improve athletic performance, prevent injuries and protect your health

Learn how to manually test for muscle strength imbalances with  education  &  certification courses offered by the Diagnosis Foundation.  This will help you identify muscle weaknesses and allow you to individualize exercise programs for your clients and friends.  This will enable you to get faster results and set you apart from others in your field.

Images courtesy:

1 – “BodyParts3D, © The Database Center for Life Science licensed under CC Attribution-Share Alike 2.1 Japan.”
2, 3 & 5 – John Wallman
4 & 6 – Used with permission of Microsoft
7 – Public Domain – National Institutes of Health

Functional Tests vs. Individual Muscle Tests: Different yet Complementary

Jumping executiveFirst, let’s describe what functional and individual muscle assessments are and their differences. Then we’ll get into why both of them are essential to a complete fitness development program.

What is Functional Muscle Testing

This is the type of assessments most of you have already experienced.  These are tests that are closely related to real world activities. such as:

  • How fast can you run?
  • How high can you, jump?
  • How much weight can you dead lift. press or pull?
  • How many of the following can you do: push ups, chin ups, squats, jumping jacks, etc. etc. etc.?

Whether you are a professional athlete, in the military, an emergency responder, in construction, a waiter, stock person, or involved in any job that requires some degree of physical capability, the scores you get on these tests will give you very good indications on how well you will do with their counterparts in real world careers.

What functional tests are not always so helpful on is distinguishing why you are getting those results.  Most of these tests will involve multiple muscles, joints and even multiple parts of the body.  Of the 5, 10 or 20 muscles involved in any of these functional tests, what is the rate limiting factor?  What muscle or joint fails first to allow you to distort into poor form, stretch a joint, experience pain or reflexive inhibition against further exertion?

Let’s take a simple functional test to demonstrate what I mean by this.  How high can you jump?  You do this functional test and receive a score of x number of inches.  Was the weak link limiting the height you were able to jump from: a weak glut max, one of the 4 hamstrings, 4 quads, soleus, gastroc, tibialis posterior or flexor hallucis longus?  Perhaps it was muscles in your back or even in your arms, etc. etc.?

If all of your muscles are well balanced, there is no weak link, continued development of height jumped may be best obtained through various jumping exercises.  If instead, all of the muscles involved in jumping are strong, but one is dramatically weak, continued jumping exercises are more likely to deliver limited improvement.

What is Individual Muscle Testing

This type of testing is not based so much on real world activities as much as it is based upon your anatomy.  These tests isolate as much as possible one muscle at a time to look for imbalances in strength.  Imbalanced muscles can be detected by comparing the strength of each muscle to its corresponding muscle on the opposite limb.  Imbalance evaluations can also be made by comparing each muscle with all of the other muscles crossing the same joint.

If you do a test on somebody’s Tibialis Posterior muscle for example and it comes up weak, that information isn’t so meaningful regarding what you will be able to do in your career.  It does tell you that your will have a weakness in one of the primary muscles that holds up the long arch of the foot and will have a tendency or outright issue with dropped arches, foot pronation, shin splints and excessive strain on the medial side of the knee.

Jumping goalie - MSGoing back to the example of the  functional test for jumping,  If all the individual muscles involved in jumping test normal, except that an imbalanced weakness is detected in the tibialis posterior, there is a significant chance that this weak link will limit jumping height.  This would tell you to put some extra time into exercises focused specifically on the tibialis posterior muscle.  It  is interesting to note that jumping exercises provide very little benefit on improving this muscle.  Correcting this weakness through a specific ankle exercise, you would typically find that jumping can improve, even though no direct jumping exercises have been done.

Functional & Individual Muscle Work is Complimentary

Functional and individual muscle testing and exercise activities are complimentary with many options for integrating both of them.

Implementation – For example, one option for how trainers could use individual muscle strength testing along with functional testing is: start each new client with a screen of individual muscle strength tests.  Any weakness identified are brought up to appropriate strength 1st through individual muscle strength exercises.  Then, you would proceed with functional testing and exercises to achieve your client’s goals.

The transition from individual muscle activities and functional activities need not be discreet, but could overlap with a gradual shift in emphasis.  Periodic testing of your client’s individual muscles would assure that imbalances are not developing from the inherent variability of muscular physiological responses to exercises, client exercise preferences or injuries.

Benefits to Trainers – The implementation example above demonstrates how you would be in a position to achieve superior results through a more versatile range of exercise programs.  This type of testing also enables clients to clearly see which muscles are weak and know that they receive the needed exercises.  This will help the client avoid painful exercises by avoiding activities that exceed what the weak links can handle, but will also increase client satisfaction, compliance and results.  All of these factors combined, fosters your ability to see more clients visits and receive more referrals.

Seminar - MSEducation

The Diagnosis Foundation offers courses on individual muscle strength testing in many different formats.  These courses are available for individuals or on a group basis, at our locations or through your own venue.

Weak fibularis tertius muscle leads to…

Peronius tertius - 1.4 - BP3DWhen the fibularis tertius is weak, what kinds of performance and health issues can you get?  Let’s look at Fibularis Tertius (FT) anatomy, actions, measurement methods along with the implications weak FT strength can have on your athletic performance and health.

Note: The Fibularis Tertius is the muscle in red in the drawing and is also known as the Peroneus Tertius muscle.  The fibularis tertius terminology has an advantage when learning anatomy in that it indicates the muscle is on the fibula side of the lower leg.


The FT is located on the lateral side (outer side or side with the fibula) in the anterior (front) compartment of the lower leg and is superficial (towards the skin).  The top of the muscle attaches to the lower 1/3 of the fibula and the deep connective tissue between the tibia & fibula known as the interosseous membrane.  The muscle runs down the antero-lateral side of the calf, connects to its’ tendon which runs just in front of the lateral ankle.   The tendon then attaches to the base of the 5th metatarsal.

Foot - eversionAction

The main action of this muscle is to dorsiflex your foot (pull the foot up) and at the same time, evert it (twist towards the outside).  This can be summarized as, “pointing your foot up and out”.

Muscle Weakness Diagnosis

Weakness in the FT can be determined with manual muscle strength testing, careful observation of ankle alignment during walking, running and at rest and other tests. Supporting information can be gained through a detailed history as well as physical examination for neurological, vascular and orthopedic signs.  Measurement of FT ranges of motion and muscle strength are available with specialized equipment such as tensiometers or isokinetic testing devices when required for more detailed examinations, insurance purposes or research.

Functional Implications

When the FT muscle is weak, you will not have the strength you should in the following situations. 1) Dorsiflexing (pulling it up) & 2) Everting the foot (twisting the sole towards the outside).

1) Dorsiflexing the foot – The FT is involved in dorsiflexing the foot (lifting the foot up).  Since there are a few other muscles that contribute to this motion, it will be rare to experience the most severe form of this condition commonly called ‘foot drop’ unless these other muscles are weak as well.

What is more likely to be experienced by the person with only FT weakness is poor control of the ankle when doing dorsiflexion which require strength or speed.  Soccer athletes will have difficulty kicking a ball accurately or powerfully forward and to the outside. Skiers, skaters and dancers will have ankle control issues and stability will be impaired in the forward to backward plane or on the diagonal.

When FT weakness is more pronounced, the foot will tend to drop slightly and invert (sole twist to the inside) when lifting the foot up.  This can result in more frequent tripping by catching the small toes on the swing through phase of walking or running.

 Snow skiier - MS3) Eversion of the foot – The FT also everts the foot (twists the sole towards the outside).  Having adequate strength in the FT is thus critical in any activity that requires maintaining lateral ankle stability.  For example, running over rough terrain, sticking a landing in gymnastics or ‘holding an edge’ when snow skiing.  One legged stance balance and strength will be impaired for dancers and this will be a critical factors for seniors who are looking to prevent traumatic falls.

Injury Susceptibility

People with weakness of the PT, will be much more susceptible to 1) lateral ankle sprains & 2) Shin splints & anterior compartment syndrome

Ankle region - lateral - MS Clip art1)  Lateral ankle protection – The lateral ankle is particularly susceptible to sprains as the ligaments supporting that side are much weaker than on the medial ankle.  Roughly 80-85% of all ankle sprains happen on the lateral side.  Considering that the number of ankle sprains in the US are between 1 & 10 million per year, this is a very substantial number.

The relatively small FT is the only muscle that supports the lateral ankle when the foot is dorsiflexed (foot pulled up).  People with a weakness of the FT will be much more likely to experience a lateral ankle sprain as they do not have the strength to recover rapidly enough after experiencing an ankle deviation which threatens the ligaments.

When a sprain occurs, at least one of the fibularis muscles which protect the lateral ankle are typically damaged (i.e. fibularis: longus, brevis or tertius).  Rather frequently, therapy is only oriented to recovery of the ligament.  The joint is immobilized or supported with athletic tape, rigid or semi-rigid device until the ligaments can take weight bearing without difficulty.  Whichever of the fibularis muscles receives damage will also require rehabilitating with specific exercises to prevent a chronic weakness of the FT and increased susceptibility to recurring ankle sprains, instability and  performance degradation.

2) Shin splints & anterior compartment syndrome –  Shin splints are a fairly vague term used to describe pain in the anterior portion of the lower leg.  This will result when any of the muscles in that region receive damage otherwise known as a muscle strain.  The FT is one of the muscles in this region that can frequently be involved due to it’s relatively small size.

Slide into base - MSDirect action damage – to the FT can come about through vigorous kicks to the outside or forcible plantar flexion (pointing the foot down) particularly when simultaneously twisting the foot to the inside (see arrow).  Overexertion of the FT can also result from trapeze artists attempting to hang from their feet without adequate exercise preparation.

Indirect action damage – to the FT is also commonly experienced though it’s involvement in ‘breaking’ or deceleration of the foot at the end of vigorous toe off maneuvers (jumping)  The FT will be most susceptible during jumps which also involve lateral movement to the same side (i.e. jumps up and to the right will more likely require right FT braking).

With people who do not have a FT of comparable strength to their toeing off jumping muscles, they can literally rip their own FT when they attempt to put the ‘brakes’ on their foot motion at the end of a jump.  The muscular strain damage and resulting pain or ‘shin splints’ can last for days to months depending on the severity.

Anterior Compartment Syndrome – Muscles in the anterior (front) of the lower leg are also susceptible to a particularly nasty complication from muscle strains.  This region has a relatively tough membrane encasing the muscles that does not expand readily when there is swelling.  This results in the thinner walled veins and lymph vessels that are contained within the muscles encased by this membrane to collapse as the swelling pressure increases from a strain.

The thicker walled arteries however, continue to deliver blood.  This results in further increase in pressure in the anterior compartment. This vicious cycle can continue until there is a severe increase in pressure which can compromise all circulation and  threaten oxygen starvation and tissue death.  This complication is known as ‘anterior compartment syndrome’ and can progress to the point of a medical emergency.

Chronic Weakness 

Learn how to test for muscle strength imbalances with education certification courses offered by the Diagnosis Foundation.  Then you can help identify muscle weakness early, when correction takes the minimal effort.

Images courtesy:

1 – “BodyParts3D, © The Database Center for Life Science licensed under CC Attribution-Share Alike 2.1 Japan.”
2 – John Wallman
3, 4, 5 – Used with permission of Microsoft

How many ligaments are in the knee?

X-Ray of a KneeSome joints are ‘held together’ primarily by the shape of the bones (i.e. hip).  Other joints are primarily ‘held together’ by muscles (i.e. shoulder).  The knee is held together primarily by ligaments.

There are 4 main ligaments in each knee.  They are:

  • Anterior cruciate ligament
  • Posterior cruciate ligament
  • Medial collateral ligament
  • Lateral collateral ligament

If any of these ligaments becomes too long through stretching,, abnormal biomechanics or trauma, the knee will have difficulty tracking correctly.  The bones will tend to move in ways where they can pinch, scrape or tug on other tissues that normally don’t receive this much stress.

Of particular concern is abnormal motions that result in damage of the minisci.  When these get damaged, it is typically thought of as permanent and the beginning of the long slow process of developing osteoarthritis of the knees.  Prevention is by far the best approach to long term knee health.

One way to maximize knee health is by taking care to prevent the ligaments of the knees from becoming too long through abnormal biomechanics.  Pathologically stretching out  the ligaments of the knees through abnormal biomechanics is actually quite a common situation.  Think of how many people you know with: dropped arches; feet that pronate; ankle sprains; achilles tendonitis; ‘knock knees’; bow legged; tight hamstrings; weak quadriceps, etc.  Each of these can puts excessive strain on the ligaments of the knees which will eventually result in them being lax and causing abnormal knee mechanics.

Prevention can be assisted by regularly checking for muscle imbalances in the knees, ankles and hips.  When caught early enough, correction can be as simple as a few weeks of the right exercise.  Let go just a little too long, and you could be looking at a lifetime of problems.

  1. Are you a health care provider who does individual muscle strength testing or treatment?  Consider joining our free DxProvider Data Base service.  Fill out two short forms and you will be on our referral list when we receive inquiries for your type of expertise in your area.
  2. Contact the DxF to schedule a screening event that evaluates muscle strength balance in the knee region. 

How many bones does the human body have?

Skeleton - MSFrom the smallest, the stapes in the inner ear to the largest, the femur or thigh bone.  The average human, adult body has 206 bones.

The number can vary slightly with each person.  Some people have bones that do not form correctly or can be missing at birth.  Others will develop extra bones within tendons similar to the patella (or knee cap).  Each bone is controlled by one or more muscles to help it move properly with the adjacent bones or soft tissue.  If the muscles controlling any bone are not working at the correct strength, the bone will not move properly or will be pulled out of position.

How do you know if your joints are balanced to keep your joints stable and healthy? You can have a Balanced Muscle Screening (BMS) for free!

Read about how you can set yourself apart and begin a new lifestyle as a Balanced Muscle strength screener. New careers! Or offer your clients Balanced Muscle Strength screenings to develop routines with meaning rather than compromise membership price.

List of bones (From Wikipedia)


Cranial (8)

Facial bones (14):

In the middle ears (6):

In the throat (1):

In the shoulder girdle (4):

In the thorax (25):

In the vertebral column (24):

In the arms (2):

In the forearms (4):

In the hands excluding sesamoid bones (54):

In the pelvis (4):

In the thighs (2):

In the legs (6):

In the feet excluding sesamoid bones (52):