Fat pad inflammation
What is Fat Pad Inflammation?
The fat pad is a lump of fatty tissue inside the knee that sits directly behind (deep to) the patellar tendon. It is not just an inert lump of fat – it is actually rich in nerves and blood vessels, and it is very sensitive. Nobody is 100% of the exact function of the fat pad, but it probably acts as a cushion at the front of the knee, preventing the patellar tendon and the bottom part of the patella from rubbing on or pinching the structures at the front of the middle of the knee (such as the front of the ACL) in deep knee flexion (bending).
The vast majority of the time, the fat pad doesn’t cause any kind of trouble at all. However, in some people the fat pad can become inflamed, in which case it can cause pain at the front of the knee.
Fat pad inflammation can occur in anyone. However, it tends to occur mainly in sports people, particularly with sport/exercise that involves a lot of repetitive bending of the knee.
Fat pad inflammation causes an aching, burning or pinching pain at the front of the knee, just below the level of the kneecap, directly behind the patellar tendon. This pain comes on particularly with exercise such as running or squatting. Generally, fat pad inflammation does not cause mechanical-type knee symptoms such as giving way or locking, and it tends not to cause any particular swelling in the joint. Examination of the affected joint is often fairly unremarkable, except for perhaps some minor tenderness around the front of the knee (behind or either side of the patellar tendon) that is sometimes worse with deep knee flexion.
Fat pad inflammation quite often occurs in association with other synovial-type pathologies such as medial plica syndrome (CLICK HERE for information about medial plica syndrome).
Investigation of possible fat pad inflammation includes screening for other pathologies around the front of the knee that might give similar symptoms, and therefore includes X-rays, MRI and Ultrasound. The advantage of MRI is that it shows pretty much everything in the knee, including all of the deep structures. The advantage of ultrasound is that ultrasound is the most sensitive imaging test for spotting inflammation in the more superficial structures, nearer the surface (such as the fat pad). Also, with ultrasound, if the radiologist does find evidence of fat pad inflammation then they can potentially go ahead directly with an ultrasound-guided steroid injection into the fat pad, which normally helps improve or sometimes even cure the symptoms.
The treatment of fat pad inflammation really does depend on how bad the patient’s knee pain and functional restrictions are, and on what potential treatments might already have been tried. Generally, it is normally wise and appropriate to start with the less-invasive treatments, and then work one’s way up towards the more invasive treatments depending on how the knee responds. The standard order of treatment is:-
1. Rest, ice and anti-inflammatories
3. Ultrasound-guided steroid (cortisone) injection (which acts as a very powerful anti-inflammatory - having this performed in an X-ray Department by a specialist Consultant Radiologist under ultrasound guidance is by far the best way to do it, as the ultrasound confirms the actual diagnosis plus it means that the injection is put exactly into the precise correct area.
4. Knee arthroscopy and trimming + cautery of the thickened and inflamed portion of the back of the fat pad.