Clinical improvements are not explained by changes in tendon structure on UTC following an exercise program for patellar tendinopathy

OBJECTIVES: The aim of this study was to investigate the effects of a 4-week in-season exercise program of isometric or isotonic exercises on tendon structure and dimensions as quantified by Ultrasound Tissue Characterization (UTC).

DESIGN: Randomized clinical trial. Volleyball and basketball players (16-31 years, n=29) with clinically diagnosed patellar tendinopathy were randomized to a 4-week isometric or isotonic exercise program. The programs were designed to decrease patellar tendon pain. A baseline and 4-week UTC scan was used to evaluate change in tendon structure.

RESULTS: No significant change in tendon structure or dimensions on UTC was detected after the exercise program, despite patellar tendinopathy symptoms improving. The percentage and mean cross-sectional area (mCSA) of aligned fibrillar structure (echo-types I+II) (Z=-0.414,p=0.679) as well as disorganized structure (echo-types III + IV) (Z=-0.370,p=0.711) did not change over the 4-week exercise program. Change in tendon structure and dimensions on UTC did not differ significantly between the groups.

CONCLUSION: Structural properties and dimensions of the patellar tendon on UTC did not change after a 4-week isometric or isotonic exercise program for athletes with patellar tendinopathy in-season, despite an improvement of symptoms. It seems that structural improvements are not required for a positive clinical outcome.