Infrapatellar Fad Pad

The infrapatellar fat pad is a soft tissue that lies beneath the patella (kneecap) separating it from the femoral condyle (end of the thigh bone). In situations where forces are directed at the patella it acts as a shock absorber, thus protecting the underlying structures.

What is Fat Pad Impingement?

In the case of a forceful direct impact to the kneecap, the fat pad can become impinged (pinched) between the femoral condyle and the patella. As the fat pad is one of the most sensitive structures in the knee, this injury is known to be extremely painful. This condition is normally long-standing as it is aggravated by extension (straightening) of the knee joint. Hence the fat pad comes under constant irritation and may become significantly inflamed.

Symptoms of Fat Pad Impingement

• Tenderness and/or swelling around the bottom and under the kneecap
• Patients may have a history of knee hyperextension (genu recurvatum)
• In some cases the bottom of the kneecap may be tilted outwards due to swelling underneath
• Positive Hoffa's test (with the patient in lying with their knee bent, the examiner presses both thumbs along either side of the patellar tendon, just below the patella. The patient is then asked to straighten their leg. Pain and/or apprehension of the patient is considered a positive sign for fat pad impingement)

Treatment of fat pad impingement.

Treatment of this condition is normally by conservative methods which may include:

• Rest and avoiding aggravating activities.
• Ice or cold therapy to reduce pain and inflammation.
• Electrotherapy such as ultrasound and TENS.
• Muscle strengthening exercises to maintain the strength and fitness of the surrounding muscle groups
• Taping the patella is known to be highly effective in fat pad impingement. One method involves taping the upper surface of the patella to allow more space for the structures beneath the lower surfaces i.e. the pat pad, and so putting them under less stress.

If conservative treatment does not work then surgery may be advised. This may involve the complete or partial removal of the fat pad itself.

Fat pad: Sagittal proton density (A) and T2-weighted (B) MR images of the knee demonstrate distortion and distension of Hoffa's fat pad. Both low and high signal intensity stranding of the infrapatellar fat is demonstrated.

Source: Medcyclopaedia TM
Amersham Health.