Athletes and Pathokinematics - Part II - Foot & Ankle

This week we will be looking at what is the impact of these pathokinematics on the various links in the kinetic chain?  To answer this question, let’s look in detail at the influence various types of pathokinematic movement patterns have on specific parts of the lower extremity, which for the purposes of this discussion will include the following:

·       Foot and Ankle

·       Lower Leg

·       Knee

·       Hip

·       Lower Back and

Sacrum

Pathokinematics Impact on the Foot and Ankle: 

Much like the analogy we used above with the car and tires, the foot is a very complex structure that is designed to be loaded in a very predictable fashion.  The foot is composed of 26 bones, 33 joints and over 100 muscles, ligaments and tendons.  It is the first shock absorber in the kinetic chain and its complexity of bones, ligaments, tendons, muscles, and joints, and the requirements made of it in order to allow the body to walk, run and stand, among other activities, mean that it must continually absorb tremendous amounts of force. 

Studies show that ground reaction forces, particularly as seen in high impact sports such as basketball, volleyball, cheerleading and gymnastics, can vary from 3 to as great as 6 times body weight[i].  Anything that alters the mechanics of the foot or the movements that occur at the foot can result in abnormal force attenuation with resulting breakdown in the tissues that can lead to acute or chronic injury.  In a closed kinetic chain, where the feet are in contact with the ground and we see pathokinematics at the foot or ankle, or anywhere in the body above the foot and/or ankle, it is easy to see the tremendous impact these poor movement patterns can have on the alignment and structures of the foot and/or ankle.

The pathokinematics that we typically see at the foot and ankle are often associated with pronation at the foot and ankle.  This can result in abnormal force attenuation on the tissues of the foot and ankle, the effects of which are significantly increased during high impact sports.  This can lead to several problems including, but not limited to:

1.     Plantar Fasciitis – the plantar fascia is a thick connective tissue which supports the arch of the foot.  Functionally, it serves to support the arch and to absorb force at the foot as the foot comes into contact with the ground.  Plantar fasciitis results from pathokinematics when the foot pronates excessively.  This results in the medial arch of the foot dropping more than it would normally or at a faster pace than normal.  This causes a significant tensile stress to the plantar fascia as well as a decrease in the amount of energy absorbed by the structure, for which it is partially designed, potentially resulting in two things:

a.     Excessive tensile stress over time can result in an inflammatory response in the plantar fascia called plantar fasciitis.

b.     Decreased energy absorbed here means that more force is then absorbed higher in the kinetic chain, beginning at the calcaneous, ankle, and moving to the knee, hip and lumbar spine. 

 

2.     Neuroma – a neuroma is a thickening or enlargement of a nerve.  In the foot, a common presentation of this is a neuroma of the intermetatarsal plantar nerve on the ball of the foot.  This is commonly referred to as a Morton’s Neuroma and presents as an enlargement, pain or tingling between the 3^rd and 4^th metatarsals on the plantar surface of the foot.  Athletes will often refer to this as pain at push off or a sense of a “BB” in the ball of their foot.  While these often result from foot deformities, flat feet or activities which cause repetitive stress to the ball of the foot such as high impact sports, pain, injury or excessive pronation (pathokinematics) can add to abnormal force attenuation of the forefoot and increased stress on the intermetatarsal plantar nerve.

3.     Retrocalcaneal bursitis – the retrocalcaneal bursa is a bursal sac that is between the calcaneous and the Achilles tendon.  Excessive pronation, causes increased tensile stresses to the plantar fascia and wear and tear on this bursal sac.  Excessive wearing over time can result in an inflammatory response which is referred to as retrocalcaneal bursitis.

4.     Achilles tendonitis and tendinosis – the Achilles tendon is tendon that attaches the gastrocnemius, soleus and plantaris muscles to the calcaneous.  Excessive pronation of the foot can result in excessive stress to the Achilles tendon resulting in tendonitis or tendinosis.  This can also be the result of several other conditions such as:

a.     Increased force attenuation – due to the increased pronation at the foot and a resulting decrease in force that is absorbed by the plantar fascia, mid-foot and rear foot, the Achilles tendon is then exposed to higher forces.  Over time this can result in tendonitis (inflammation of the tendon) or tendinosis (a long standing problem where there is breakdown of the collagen, scar formation or calcification) of the Achilles tendon.

b.     Prolonged or worsening plantar fasciitis - the plantar fascia is continuous with the Achilles tendon via the fascial sheath and as a result, excessive stresses to the plantar fascia, prolonged and or worsening plantar fasciitis can often result in Achilles tendonitis.  The knowledge of this connection is often used in treatment of plantar fasciitis.  Knowing this, if the toes are dorsiflexed, the plantar fascia tightens.  If a tensile force (stretch) is then generated in the Achilles tendon, it will increase tensile strain in the plantar fascia and vice versa. 

c.     Pain – pain resulting from plantar fasciitis or retrocalcaneal bursitis (as the result of excessive foot pronation) can result in compensatory movement or gait.  These additional compensatory movements, in themselves, can add to an already increased force attenuation at the Achilles tendon.

Consider a case study for an in-depth look at the impact pathokinematics can have on the foot and ankle.  At left is a cheerleader who demonstrates a significant lateral shift when squatting.  At the end range of motion of her squat, she loses control at both ankles, and excessively pronates into pes planus.  This is much more evident on the right than the left in this photo.  The athlete here is highly trained and very fit, but complains of ankle pain, especially on the right with competition.  She also complains of difficulty reaching peak vertical height when jumping as a flyer.  Obviously, in cheerleading, this is an important measure of success overall, and is critical for many specific cheerleading activities.

This individual also demonstrates a significant lateral shift when descending (eccentric movement) as well as with ascent (concentric movement) during the squatting motion, which is indicative of decreased lumbopelvic proprioception.  If combined with adduction of the hip during single leg squat movements, this can indicate gluteus medius weakness on one side.  Since she demonstrates excessive pronation bilaterally with squat and with a step up motion, we can also suspect weakness in the musculature of the foot, ankle and lower leg.  Weakness in this area can cause extreme pes planus during these motions and add to the hip adduction we see in single leg squatting motions.  In this example it is evident that the right is weaker than the left, secondary to the magnitude of pronation. 

Because the ankle is a hinged joint, it is designed to move the foot in four primary directions:  plantar flexion, dorsiflexion, inversion, and eversion.  When the foot is forced to pronate to this degree, as in this example, there is a tremendous amount of stress on the tendons and ligaments of the joint which serve to stabilize it in all three planes of motion.  These include the anterior talofibular ligament and calcaneaofibular ligament as well as the peroneal tendons, and the Achilles tendon.  The gastrocnemius and soleus calf muscles that attach at the ankle, as well as the calcaneus and retrocalcaneal bursa are at risk as well.

So what kinds of injuries is this athlete likely to incur?  She certainly is at risk for ankle sprains, stress fractures (shin splints) and fractures, especially upon hard landings from jumps.  She is also subject to tendonitis or inflammation of the tendon, which can occur in the Achilles tendon, the posterior tibial tendon, or the peroneal tendon in this case.  If tendonitis occurs, especially in the Achilles tendon area and the athlete does not rest, there is increased risk of the tendon rupturing or tearing, which usually requires surgery to repair.  Other possible injuries this athlete could sustain include breaks to the metatarsal bones (toes), the calcaneous (heel bone) or lateral or medial maleolus, or tearing and/or inflammation of the plantar fascia.  Because of the loss of kinetic energy across the system, and the associated adduction of the knee in a closed kinetic chain, this athlete could also be more susceptible to injuries of the ACL and medial and lateral meniscus at the knee which have to work harder due to an unstable surface at the foot and ankle. 

As noted before, this athlete will be limited on peak vertical height when jumping as long as the kinetic chain is interrupted in this fashion, and energy is absorbed at the ankle instead of passing through the foot to the ground upon take off.  Her endurance will be similarly limited because of a lack of symmetrical strength in the lower extremity and the greater force that is required to obtain heights that would normally not take as much force.  Her ability to participate effectively in stunts that require jumping and bounding motions is therefore compromised.

 
Next week we will look at the impact these movements have on the knee.  If you like what you read the biggest compliment you can give to us is to share the passion.  Follow us on Twitter @ACL_prevention or on Facebook at Athletic Therapy Services.  Remember #MoveRight, last longer and perform better!

Dr. Nessler is a practicing physical therapist with over 17 years sports medicine clinical experience and a nationally recognized expert in the area of athletic movement assessment.  He is the developer of an athletic biomechanical analysis and author of a college textbook on this subject.  He serves as the National Director of Sports Medicine for Physiotherapy Associates, is a Safety Council Member for USA Cheer National Safety Council and associate editor of the International Journal of Athletic Therapy and Training.