Intratendinous ganglion cyst of the semimembranosus tendon.

Intratendinous ganglion cyst is a very rare lesion with an unknown aetiology that originates within the tendon. We encountered a case of 43-year-old woman who complained of a palpable, non-tender mass in the thigh with increasing swelling. An intratendinous ganglion cyst in the semimembranosus tendon of the lower extremity was diagnosed and located by ultrasound and MRI. Nine months after a surgical excision, there were recurrent ganglion cysts along the semimembranosus tendon. We describe this case with a review of the relevant literature.