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Pes Anserenus. Medial Knee Pain

Anatomy
Pes Anserenus is the term given to the common attachment of three muscles that insert into the tibia, just below and medial to the knee (see figure 1). These three muscles are from anterior to posterior the Sartorius, Gracilis and Semitendinosus (see figure 2). All three have separate origins and separate nerve supplies but converge about the medial knee before inserting into the Pes Anserenus.

Further anatomical considerations
The origins of these three muscles are quite diverse. Anterior (in front of) to the hip, originating from the anterior superior iliac spine (boney prominence at the front of the hip) is the sartorius. Deep in the adductor (groin) region, originating from the inferior ramus of the pubis, is the Gracilis. And the Semitendinosus is one of the hamstring muscles and originates from the Ischial Tuberosity (the ‘sit bone’ or the boney prominence at the base of your buttocks). All three muscles are superficial and can be palpated easily although the Gracilis is quite difficult to identify as it is quite thin.
Importantly, there is a bursa lying underneath the three tendons as they attach into the tibia. Bursa are fluid filled sacks that can be found all over the body and are there to protect against two unyielding tissues frictioning on each other and causing tissue damage. In this case the two surfaces are the three tendons (as they traverse over the medial tibia) and the boney surface of the tibia itself.

Function
As a group the sartorius, gracilis, and semitendinosus muscles are primary flexors of the knee. These 3 muscles also influence internal rotation of the tibia and protect the knee against rotary and valgus stress.
The individual function of the these three muscles is quite diverse. In brief, the sartorius which has a nick name of the ‘tailors muscle’ acts to hip flex (bring knee towards thorax) and laterally rotate (rotate the thigh outwards) the hip, as well as flex the knee (bend the knee) and laterally rotate the tibia (outwardly rotate the lower leg). It was called the ‘tailors muscle’ as this was the position tailors would sit in to sew.
The Gracilis is one of the long adductor group and is thought to adduct (bring towards the midline) the thigh as well as flex the thigh.
The Semitendinosus being one of the hamstring group helps extends the thigh as well as being a stabiliser of the medial thigh.

Pathologies/Injury
The Pes Anserenus is not a commonly discussed area unless there is pathology to the area. The most common injury is to the bursa that lies under the tendons and over the tibia. What is assumed to occur is that the friction between the tendons and the tibia becomes too much for the bursal tissue to handle and it fails and becomes inflamed. The result is a painful, aching sensation that is sometimes red, hot and swollen (inflamed) but not always. Running becomes painful and pain only subsides when you stop. Rubbing the area will further inflame the area as you will be further irritating the bursal tissue.

Treatment
Depending on the severity of the bursitis, you may have to decrease or stop running for a brief to extended time to allow the bursa to settle. Because the bursa in this area is quite superficial, topical anti-inflammatories may help. Simply place a large dobble of gel over the painful site (don’t rub it in or you risk further irritating the bursa) and put glad wrap over the area to keep it on the focal area and off your bed sheets. Sleep in this over night for a couple of nights.
Before diving into stretching it would be best to consult your Health Practioner. Stretching may further compress the tendons over the angry bursa and exacerbate the problem. Figuring out why these three tendons are creating excessive friction is necessary to objectively treat this condition. It quite simply might be one or all three of these muscles become tight and shortened or it could be a more complex pelvis issue that your Practioner can assess and treat.

Self Treatment
Instead of stretching these muscles and risking further irritating the bursa, try self massage to these three muscles. Use some form of cream, sorbelene for example and slowly glide your thumbs or fingers along these muscles. Identifying them may be a bit tricky so either consult someone to help you out or go for the global approach and work the surrounding area, as close to these muscles as possible, spending time on what you palpate as tight. Alleviating this muscular tightness may help reduce the load on the bursa that is inflamed but keep in mind that once a bursa is angry, they tend to take a while to settle down. And note, if self massage to these muscles makes things worse, stop and consult your Health Practioner.
Cortisone may be an option for persistent Pes Anserenus bursitis. Clinically this type of cortisone injection shows excellent results but of course; try your conservative treatment first.

Summary
Your Pes Anserenus is the attachment of three thigh muscles that traverse from the pelvis to the medial lower knee. The bursa that stops over frictioning of the tendons over the tibia may become inflamed if the friction is excessive. Sort advice before stretching but certainly self massage the muscles involved.

Happy running.