Popliteus tendinitis

Pain around the lateral aspect of the knee is a common occurrence, where popliteus tendinitis is a relatively infrequent condition. The symptoms can be quite disabling, especially to the serious athlete. This problem often occurs in long distance runners or in joggers who train on a sloping hard surface, especially downhill. It is also seen in soccer and recreational mountain walking. Complaints are more often in patients with genua vara.

Anatomy

The popliteus muscle has two origins, femoral and meniscal. The femoral arises by a strong rounded tendon from the lateral condyle of the femur. The meniscal by tendinous fibers from the back of the lateral meniscus. The muscle passes downward and medially to the tibia.
The popliteus rotates the femur laterally when the tibia is fixed. It pulls the lateral meniscus backward at the beginning of flexion. Presumably it prevents the femur from sliding forward on the tibia.
The popliteus muscle plays a major role in the active performance of the pivot shift maneuver. This makes patients with anterolateral rotatory instability form injury of the anterior cruciate ligament prone to complaints of the popliteus.

Diagnosis
Provocation of complaints occurs by active flexion and internal rotation of the lower leg against resistance. A tender point can be found on the femoral origin just before the lateral collateral ligament.
Ultrasound is the imaging modality in favour to make the diagnosis and to distinguish tendinitis from a meniscal cyst or synovial hemangioma.

Treatment
The local treatment, antalgic and antiinflammatory, must be followed by a modification of the training habits. Local application of ice, friction's and ultrasound can be useful. Sometimes a local injection with corticosteroids is needed. For secondary prevention strenghtening of the hamstrings is needed.

References
Howard, CB. Bonneh DY. Nyska M. Diagnosis of popliteus tenosynovitis by ultrasound. JOSPT 16 (2) 1992, 58-59.
Peterson, L. Pitman MJ. Gold J. The active pivot shift: the role of the popliteus muscle. American J of Sports Med 12 (4) 1984, 313-317.