Between January 1995 and Jul 1997, 474 patients with anterior knee pain res
istant to conservative treatment were referred for MR of the knee. The MR e
xamination consisted of routine sequences with an additional patellofemoral
dynamic examination using a technique that has been developed at instituti
on. The dynamic study examines both knees simultaneously, with the patient
supine and the quadriceps loaded. No gating or restraint apparatus needed.
Patellar subluxation or tilt was present in 188(40%) of cases, bilateral in
104 and unilateral 84 cases (right 39, left 45). It was classified as mild
51%, moderate in 39% and severe in 10%. Subluxation was more prevalent in
females than males (42% vs. 37%) and this was most obvious in the severe gr
oup where 68% were female. In 90 knees seat random, four measurements of pa
tellofemoral morphology were obtained using reconstructed images from a vol
ume gradient echo sequence. These measurements were correlated with the deg
ree of subluxation or tilt. A tibial tubercle distance greater than 20 mm,
a femoral sulcus angle greater than 150 degrees, sulcus depth less than 4 m
m were specific for sublaxation but no measurement proved to be sufficientl
y sensitive to preclude a tracking study. MRI can be used to define more pr
ecisely the anatomy of the extensor mechanism and its relationship to the f
emur and tibia, in both a static and dynamic setting. In this way, patients
with anterior knee pain can be classified more accurately and the outcomes
of treatment more reliably assessed.