One of the most common causes of knee pain is irritation of the patellofemoral joint. Almost all the structures around the patellofemoral joint can be palpated to help one localize best the area of the patient’s pain.
The medial suprapatellar plica is palpated by rolling ones finger along the edge of the medial femoral condyle between the medial border of the patella and the adductor tubercle. There is a normal band of tissue in this area, which everyone has, which constitutes a fold in the normal joint lining. The tissue in this location can become quite irritated when there are problems with the muscle strength of the patellofemoral joint or due to other irritation in the joint.
Palpation of the hamstring attachments are also very important. Particularly, the pes anserine bursa can be quite tender to palpation. This is where the hamstring tendons attach over the superficial medial collateral ligament on the medial aspect of the proximal tibia. In addition, the FCL – biceps bursa, located just proximal to the fibular head, the semimembranosus bursa, located on the posteromedial aspect of the tibia and the deep infrapatella bursa, which is located just proximal to the tibia tubercle can be palpated. One should always palpate these areas when there is concern for patellofemoral joint pain to determine if the patient has tight hamstrings and irritation of these attachment sites.
Patellar tendinopathy is also a common problem which can be determined by palpation. Patellar tendinopathy is due to degeneration and potential partial tearing of the patellar tendon at its attachment site on the distal pole of the patella. This can usually be easily palpated when the knee is in full extension. Since this tendinopathy occurs in the deepest fibers of the patellar tendon, when one flexes their knee to 90° there should be less pain to palpation with patellar tendinopathy because the more anterior fibers of the patellar tendon become tight and it is harder to palpate the area of the tendinopathy.
Other areas of pain around the patellofemoral joint include the prepatella bursa, which is the potential space over the front of the patella, and the infrapatellar branch of the saphenous nerve. The infrapatellar branch of the saphenous nerve crosses just distal to the joint line and over the more distal aspect of the patellar tendon. Almost all patients who have an ACL patellar tendon autograft reconstruction or a meniscus repair will have some numbness over the anterior aspect of the knee which is unavoidable, as part of this surgery. Sometimes when the nerve grows back (which it always does), the newer fibers become like an entangled mesh of spaghetti and can cause some pain. Palpation at this area may be useful to determine if this is a painful neuroma.