CORRELATION OF MR-IMAGING AND PATHOLOGICAL FINDINGS IN ATHLETES UNDERGOING SURGERY FOR CHRONIC PATELLAR TENDINITIS

OBJECTIVE. Jumper's knee, or chronic patellar tendinitis, can be a sou rce of considerable pain in athletes. The changes that occur with shea ring of the tendinous fibers from repeated microtrauma can progress to significant degeneration and increase the risk of tendon rupture. In order to better understand this phenomenon, a correlative study relati ng the MR imaging and pathologic findings was performed. SUBJECTS AND METHODS. Nine high-performance athletes 18-22 years old (mean age, 20 years) underwent operation of 11 knees far long-standing jumper's knee . The average period of symptoms was 3 years (range, 2 to 6 years). MR knee examinations were performed before surgery in all athletes. The symptoms, MR findings, and pathological findings were correlated, RESU LTS. There was focal thickening in the proximal one third of the patel lar tendon (range, 9-16 mm; mean, 12 mm) in all II knees, involving th e medial portion of the tendon in 10 and the center in one. On proton- density-weighted MR images, all knees demonstrated a focus of abnormal signal intensity in the proximal one third of the patellar tendon, On T2-weighted MR images, 10 knees demonstrated abnormal signal intensit y; eight were isointense to that seen on proton-density-weighted image s, and two were relatively hyperintense. Ten tendons demonstrated a po orly defined posterior margin, Pathologically, the areas of abnormal s ignal intensity corresponded to tissue containing tenocyte hyperplasia , prominent angiogenesis with endothelial hyperplasia, toss of longitu dinal collagenous architecture, and microtears with collagen fiber sep aration. Hyaline degeneration was present in specimens from every pati ent. CONCLUSION, In athletes with chronic patellar tendinitis, areas o f abnormal signal intensity on MR imaging corresponded to degenerative pathologic changes consistent with angiofibroblastic tendinosis. In n early all patients, the tendon thickening occurred eccentrically. Disp roportionate medial tendon thickening may be related to unequal tensil e forces across the knee joint, resulting in greater stress on the med ial portion of the extensor mechanism of the knee.