Case 13

History
Anterior knee pain.

Diagnosis
Findings compatible with patellar tendon–lateral femoral condyle friction syndrome.

Findings
Axial and Sagittal T2 fat saturated images show focal abnormal high signal intensity in the superolateral aspect of Hoffa’s fat pad.

Discussion
Patellar pain and anterior knee pain are common presenting problems encountered in primary care and orthopedic clinics. Patients typically present with knee pain exacerbated by hyperextension accompanied by focal point tenderness at the inferior pole of the patella. The fat pad is thickened resulting in difficulty palpating the patella on the affected side.

Imaging findings include a focal area of abnormal signal intensity in or surrounding the inferolateral aspect of the patellofemoral joint including lateral portion of the infrapatellar fat pad. This is seen as high signal or edema on STIR or T2 weighted sequences. Occasionally a focal lobulated mass with signal intensity characteristics of fluid or cystic change can be seen in the lateral soft tissues of the knee between the lateral femoral condyle and the lateral retinaculum.

References
Chung CB, Abdalla S, et al. Patellar tendon-lateral femoral condyle friction syndrome: MR imaging in 42 patients. Skeletal Radiology (2001) 30:694-697

Submitted by Brett Staller, M.D.
Reviewed by Paul Clifford, M.D.