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The symptoms of patellar tendinitis are relatively easy to recognize. The patient will feel pain, not directly behind their kneecap (as in the condition of chondromalacia), but just below (distal to) it. Tenderness is present within the upper (proximal) patellar tendon, and in particular where its mid-section attaches to the lower end of the patella. The patient will typically feel discomfort there if they are either trying to kneel directly on their knee or if they are placing a lot of tension on their patellar tendon. The latter occurs while running, jumping or when bending the knee and supporting one's body weight at the same time (i.e., getting into a half-squat position). In very inflamed cases, local warmth can actually be felt emanating from the tissues beneath the skin overlying the patellar tendon. X-rays are almost always normal, and only in advanced cases where significant structural tendon degeneration has occurred are MRI scans (such as the one shown in FIGURE 3) abnormal.

FIGURE 3 - Advanced case of patellar tendinitis. This MRI scan image shows a close-up, side view of the frontal region of an actual patient's knee, with the lower half of the patella ("P", above) resting against the frontal portion of the femur ("F", to the left). Below the patella one can see the patellar tendon, running downward toward the tibial tubercle (not seen). The normal portion of this patellar tendon is solid black, and looks thin and straight (double arrow). The afflicted, upper segment of tendon that attaches to the patella is swollen and has lost its normal black appearance (single arrow). The lighter shaded tendon tissue in the swollen zone represents degenerated and broken down tendon fibers. If very heavy stress is applied to a tendon in this condition, it can rupture through the degenerated zone, suddenly and unexpectedly. Urgent surgical repair would then be necessary.

Because most cases of patellar tendinitis are not advanced, and therefore not diagnosable with an MRI scan, general physicians and even orthopedic surgeons may sometimes fail to identify this common problem! While the symptoms of jumper's knee are not hard to recognize if one listens carefully to the patient's detailed description of what they have been experiencing, specific diagnostic tests are often required on physical examination to confirm the presence of this malady. If the knee is examined for proximal patellar tendon tenderness at the wrong joint flexion angle and/or with incorrect patellar posture, no tenderness may be elicited and the diagnosis may therefore be missed. During the course of rendering many second opinions over the years, I have seen a number of cases where patellar tendinitis had been mistaken for chondromalacia patella or knee arthritis, leading to an initial recommendation for an unnecessary knee arthroscopy.


® 2007. The Knee and Shoulder Centers of New Jersey and Pennsylvania.