Hoffa Pad Impingement Syndrome

There are 3 primary anterior knee fat pads, such as the quadriceps suprapatellar, pre-femoral suprapatellar, and infrapatellar retro-patellar tendon (Hoffa's fat pad), all of which may experience symptomatic impingement. The Hoffa pad, also known as the infrapatellar fat pad (IFP), is an extra-synovial, intracapsular structure that occupies most of the anterior knee compartment.  The IFP can become 1 of many causes of anterior knee pain when it becomes inflamed, leading to impingement at the tibiofemoral joint or the lateral aspect of the patellofemoral joint, known as Hoffa pad impingement syndrome. This structure is richly vascularized and innervated. Its arterial supply is from an anastomotic network of branches of the medial and lateral superior geniculate and medial and lateral inferior geniculate arteries. It is innervated by the posterior articular nerve, a branch of the posterior tibial nerve that courses through the external borders of the menisci, synovium, cruciate ligaments, and the IFP. A normal IFP attaches to the proximal patellar tendon, the inferior pole of the patella, anterior horns of the medial and lateral menisci, transverse meniscal ligament, and periosteum of the anterior tibia. The posterior aspect of this structure is lined with synovium and extends posteriorly, connecting to the intercondylar notch and, in some structures, is continuous with the anterior cruciate ligament (ACL).