Prefemoral fat pad impingement

Case contributed by Dr Dalia Ibrahim

Presentation

Anterior knee pain.

Patient Data

Age: 12 years
Gender: Female

Patella alta.

Shallow dysplastic femoral trochlea.

Focal edema signal of the fat interposed between the patella and the lateral trochlear ridge, mainly along the lateral aspect.

Annotated image

Patella alta in the first image.

Shallow dysplastic femoral trochlea in the second image.

Edema signal in the prefemoral fat pad in the third image mainly along the lateral aspect indicating lateral patellar dynamic subluxation (yellow arrows).

Case Discussion

The case shows risk factors of patellofemoral instability such as patella alta and trochlear dysplasia which can result in dynamic lateral patellar subluxation with subsequent friction and edema signal of the prefemoral pad fat mainly along the lateral aspect.

The pre-femoral fat pad or the posterior suprapatellar fat pad is located anterior to the distal femur and superior to the trochlea, separated from the quadriceps fat pad by the suprapatellar bursa.

Prefemoral fat pad impingement is caused either by:

  • prominent suprapatellar osteophyte, with edema usually in the superior aspect close to the midline
  • patellar tendon-lateral femoral condyle friction syndrome, with edema, usually occurs in the inferolateral aspect of the fat pad

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