Semimembranosus/ pes anserine bursa

Findings

Type 1

There is a history of recently taking up running, or increase in speed, in a “shuffle” runner, who often stands with the ipsilateral foot externally rotated.

Type 2

A history of a knee injury, which gradually changes its character during rehabilitation. The pain moves or a new pain appears, located over the semimembranosus bursa.

Both types may, or may not, appear locally swollen and are tender to local palpation over the bursa of hamstring insertions. Resisted hamstrings, with an externally rotated tibia and knee at 30-50 degrees flexion are painful. Check for overpronation and a weak posterior tibialis.

Cause

The pes anserine(or the semimembranosus, semitendinosus and gracilis) bursa becomes inflamed where these tendons cross the tibia towards their insertions.

Type 1

Running styles may be propulsive, pushing with the foot and calf muscle, or tractive(shuffle), pushing with the foot and calf muscle, or tractive(shuffle), with the hamstrings pulling the body up and over the foot. If the foot is externally rotated during shuffle running then the pressure over the pes anserine bursa increases and can cause inflammation.

Type 2

The hamstrings work co-actively to decelerate the swing phase and lock the knee ready for loading at impact. When the quadriceps are weak, painful, or the knee is unstable, the hamstrings are worked harder to stabilize the knee at impact, producing a secondary, compensatory injury in the semimembranosus bursa and hamstring insertions.

Treatment

Type 1

Alter the running style to a more bounding style, or correct the externally rotated foot. Anti- pronated orthotics help, and the posterior tibialis must be rehabilitated if it is weak. High knee drills will strengthen the psoas and encourage a higher knee lift during running.

Type 2

Discuss the mechanism with the athlete, who must not lock up the knee or foot on impact but learn to roll through the foot, from heel strike to lift off. The athlete should try counting, for rhythm, and match the feel of the painful leg to the good side.

Treat with electrotherapeutical modalities, such as ultrasound and laser to settle inflammation, and friction and massage for any tenosynovitis. Cortisone injection will calm the bursitis.

Sports

a)      Usually technically incorrect running style – see cause and treatment for type 1

b)      Golfers who increase “coil” tension or take away by pressing the right foot into the ground may on rare occasions produce this bursitis

The protective mechanism, type 2, is very common and, unless recognized, leads to a muddled pattern of knee pain that inhibits rehabilitation. Arthroscopy will not recognize this mechanism.

"Concise guide to sports injuries, 2^nd edition",Churchill Livingstone, Malcolm T.F. Read,  foreword by Bryan English