Tendinopathy alters cumulative transverse strain in the patellar tendon after exercise.

INTRODUCTION: This research evaluated the effect of tendinopathy on the cumulative transverse strain response of the patellar tendon to a bout of resistive quadriceps exercise. METHODS: Nine adults with unilateral patellar tendinopathy (age, 18.2 ± 0.7 yr; height, 1.92 ± 0.06 m; weight, 76.8 ± 6.8 kg) and 10 healthy adults free of knee pain (age, 17.8 ± 0.8 yr; height, 1.83 ± 0.05 m; weight, 73.2 ± 7.6 kg) underwent standardized sagittal sonograms (7.2-14 MHz linear array transducer) of both patellar tendons immediately before and after 45 repetitions of a double-leg decline squat exercise performed against a resistance of 145% body weight. Tendon thickness was determined 5 and 25 mm distal to the patellar pole. Transverse Hencky strain was calculated as the natural log of the ratio of post- to preexercise tendon thickness and expressed as percentage. Measures of tendon echogenicity were calculated within the superficial and deep aspects of each tendon site from grayscale profiles. Intratendinous microvessels were evaluated using power Doppler ultrasound. RESULTS: The cumulative transverse strain response to exercise in symptomatic tendinopathy was significantly lower than that in asymptomatic and healthy tendons (P < 0.05). There was also significant reduction (57%) in the area of microvascularity immediately after exercise (P = 0.05), which was positively correlated (r = 0.93, P < 0.05) with a Victorian Institute of Sport Assessment for patellar tendinopathy score. CONCLUSIONS: This study is the first to show that patellar tendinopathy is associated with altered morphological and mechanical response of the tendon to exercise, which is manifest by reduction in cumulative transverse strain and microvascularity, when present. Research directed toward identifying factors that influence the acute microvascular and transverse strain response of the patellar tendon to exercise in the various stages of tendinopathy is warranted.