Deep posterior knee pain caused by a ganglion of the popliteus tendon--a case report.

The most common causes of posterior and posterolateral knee pain (besides referred pain) are knee joint effusions, tendinitis of the hamstring tendons, Baker cyst (semi-membranous cyst), bursitis, meniscal pathologies such as tears and ganglions and lesions of the anterior cruciate ligament. Less common causes include popliteus and gastrocnemius tendinitis, arthrofibrosis after trauma, posterior cruciate ligament sprains, deep venous thrombosis and/or irritations of the common peroneal nerve. We present one patient with posterolateral knee pain after a minor contusion. Magnetic resonance imaging revealed a degenerated posterior horn of the lateral meniscus and a somewhat unclear polypoid structure in the intercondylar region. As the posterior component of the pain persisted even after an arthroscopic partial meniscectomy, an operative revision was performed. A small ganglion of the sheath of the popliteus tendon was found and excised. The patient was immediately relieved of his pain after this procedure. To our knowledge this is the first report concerning a ganglion of the sheath of the popliteus tendon causing posterior knee pain. A similar pathology of the popliteus tendon has been described earlier but at a different localisation (in the hiatus), simulating a parameniscal cyst.