Anatomy of the infrapatellar fat pad
The infrapatellar fat pad (commonly known as Hoffa’s fat pad) is located at the anterior (front) of the knee joint. It is a large structure positioned just behind the patellar tendon and the knee cap. It is essentially the soft bit you can push at the front of the knee under your knee cap.
The infrapatellar fat pad has a rich blood and nerve supply making this structure highly sensitive and is considered a key pain generator in many knee conditions. It is enveloped within the knee joint capsule and is intrinsically linked to both the meniscus (the shock-absorbing cushion within the knee joint) and the inner lining of the joint capsule (Bennell et al., 2004). This inner lining is known as the synovial membrane and is also a common site for inflammation and pain. An inflamed synovium is called synovitis. Synovitis can be associated with anterior knee pain (Dragoo et al., 2012).
The exact function of the infrapatellar fat pad is still under investigation, but it is believed to act as a reservoir for cells used to repair the knee after injury. It is also thought to play an important role in the shock absorption and mechanics of the knee during movement (Dragoo et al., 2012).