The influence of the lower patellar pole in the pathogenesis of chronic patellar tendinopathy.

Resection of the lower patellar pole provides good results in the treatment of jumper's knee. Therefore we hypothesized that the length of the lower patellar pole is increased in patients with chronic patellar tendinopathy. Cohort study, level of evidence 2. Between 2000 and 2005, 25 patients with chronic patellar tendinopathy underwent conservative and surgical treatment in our clinic. All of them had preoperative MRI were three independent examiners measured the Caton Index, the length and the ratio of the articular and non-articular patellar surface, tendon length and thickness and the thickness and length of the hypodens lesions in the patellar tendon. The measurements were compared with 50 MRI of a control group with no clinical patellofemoral disorders or patellar tendinopathy. Significant changes in tendon thickness (9.42+/-2.87 vs. 4.88+/-1.13; P<0.0001), a longer non-articular surface of the patella (10.62+/-2.86 vs. 7.098+/-2.53; P<0.0001) and significant higher ratio between the articular and the non-articular patellar surface (0.32 vs. 0.24; P<0.0001) were found in the jumper's knee group. No significant changes were seen in the length of the articular surface or the Caton Index. The development of chronic patellar tendinopathy in athletes might be associated with a longer lower patellar pole as patients with jumper's knee showed a longer non-articular patellar surface compared with the control group.