summary Semimembranosus tendinitis is the inflammation of the insertion of the semimembranosus tendon leading to activity related posteromedial knee pain. Diagnosis is made clinically with tenderness to palpation at the insertion of the semimembranosus tendon made worse with passive deep flexion of the knee or internal rotation of the tibia at 90 degrees of knee flexion. Treatment is nonoperative with rest, stretching and physical therapy to focus on hamstring and quadriceps strengthening. Epidemiology Demographics most common in male athletes often occurs in patients in their early thirties Presentation History of report recent increase in endurance activities (running or cycling) Symptoms pain in the posteromedial knee login to view 2 more bullets Physical exam tenderness to palpation at the tibial insertion of the semimembranosus login to view 1 more bullet provocative tests login to view 1 more bullet Imaging MRI may be helpful in making the diagnosis Nuclear imaging may be helpful in making the diagnosis Treatment Nonoperative physical therapy login to view 4 more bullets steroid injection login to view 3 more bullets