The extensor mechanism of the knee.

Disorders related to the knee extensor mechanism are common and rarely require imaging. Non specific anterior knee pain, fracture, dislocation, overuse tendinopathy and chronic patellofemoral instability are the commonest conditions encountered. Imaging is used in acute trauma, and for the assessment of cases of anterior knee pain resistant to conservative measures. The role of the radiograph is now largely restricted to cases of suspected fracture. Ultrasound is the optimum technique for suspected tendon and bursal pathology and MRI is widely used for the assessment of dysplasia and instability of the patellofemoral joint, including acute dislocation.