Superior patellar dislocation: the value of clinical examination and radiological investigation.

A 57-year-old obese woman with a history of osteoarthritis presented with an acutely painful left knee and an inability to bear weight following a twisting injury. The initial diagnosis in A&E was a ruptured patellar tendon. A more thorough clinical examination revealed a high-riding patellar with the knee hyper-extended and a patellar dimple, consistent with superior patellar dislocation.