Hoffa’s fat pad impingement syndrome (also known as infrapatellar fat pad impingement) occurs when a fat pad in your knee gets pinched between the bones of your knee joint. There are a variety of possible causes, and this painful condition often goes together with other problems in and around the knee.
This article explains the causes, how to correctly diagnose fat pad impingement, and what the treatment options are. Remember, if you need more help with an injury, you're welcome to consult one of our physios online via video call.
What happens when you have infrapatellar fat pad syndrome?
Fat pad impingement is when your infrapatellar fat pad is pinched (impinged) between your kneecap and thigh bone or between your thigh bone and shin bone.
The fat pad is meant to slide and move as you bend and straighten your knee, but sometimes its movement gets restricted due to swelling or thickening or scar tissue, causing it to get pinched when your knee is fully straightened.
Researchers are not 100% sure why this happens, but some of the causes are thought to include:
How to diagnose fat pad impingement (syndrome)?
Common fat pad impingement symptoms include:
Fat pad impingement treatment options
1. Avoid painful positions
The best way to stop irritating the fat pad is to avoid positions that cause pain. One example is standing with your knee slightly bent rather than pushed all the way straight.
However, these are temporary adjustments. Once your knee has recovered, you should start moving it through its full range of motion again, otherwise you may end up with other injuries.
2. Shoes and gait
Flat shoes usually require your knee to extend more when you walk. By wearing shoes with a slight heel (like most running shoes) or placing heel-lifting insoles into your shoes, you may be able to reduce the pinching when walking, which will help your painful fat pad to calm down more quickly.
Some patients find that taping their knees can make a significant difference. The tape is applied in such a way that it tilts the lower part of the kneecap up, which is thought to reduce the pressure on the painful fat pad.
There is currently no research available to indicate whether taping is truly effective. My advice is to test it – if your knee feels more comfortable with the tape on, then it is likely worth it.
You will need someone else to apply the tape for you, because it can be hard to relax your leg if you do it yourself. The white tape that is applied as the bottom layer is called Hypafix – it helps the top layer tape to stick better, but is also hypoallergenic and helps to protect the skin.
Here’s a video demo on how to tape your knee to relieve fat pad impingement pain. What you’ll need:
● 5 cm / 2 inch Hypafix tape for the bottom layer
● 3.8 cm / 1½ inch zinc oxide tape for the top layer
5. Anti-inflammatory medication (like ibuprofen)
Anti-inflammatory medications like ibuprofen (tablets or gel) may be useful to help reduce the inflammation and swelling. Speak to your doctor before taking any medication, as it may not be appropriate for you.
6. Manual therapy
Some patients with fat pad impingement may have a stiff kneecap that doesn’t move as freely as the one on the other leg does. In such cases, some clinicians recommend manual therapy, where the physiotherapist mobilises the kneecap. We don’t know whether this makes a difference, since there isn’t any research that has tested the effect of this versus no treatment and/or other treatments.
Stretching the quadriceps muscles is sometimes advised, since it is thought to help free up the kneecap. But this should only be tried once the acute pain has settled – stretching too early into your recovery usually makes the pain worse. You can foam roll your quads instead.
8. Strengthening exercises
It is usually best not to crack on with exercises that work the quadriceps muscles too early in recovery, as this often aggravates the pain, but you can usually get going with other muscle groups, e.g. glutes and hamstrings, in the meantime.
Muscles worth strengthening:
9. Retraining movement patterns (if needed)
This will not be necessary for everyone with Hoffa’s fat pad impingement. If your physio has found that a part of your problem is that you stand with your knee in hyper-extension or flick it back when you walk, they may teach you ways in which to unlearn those patterns. This can help you to avoid getting fat pad impingement again.
If your foot rolls in excessively (over-pronation) when you walk or run and it is not correctable through exercise alone, you may benefit from arch-supporting orthotics.
11. Corticosteroid injections
Corticosteroid injections can work very well to reduce pain, swelling, and inflammation. However, they also have unwanted side effects, the most important in this case being fat pad atrophy. This is when the steroid injection causes your fat pad to shrink, which can actually lead to even more pain.
Surgery should be left as the last resort, because it is not always successful. Keyhole surgery is recommended, where the surgeon goes in and only removes the scar tissue and thickened areas. The current recommendation is to leave the unaffected parts of the fat pad intact.