Author:

Keywords:

Science & Technology, Life Sciences & Biomedicine, Technology, Biophysics, Engineering, Biomedical, Engineering, Ultrasound speckle-tracking, Elastography, Aging, Tendinopathy, Passive knee flexion, ACHILLES-TENDON, IN-VIVO, JUMPERS KNEE, ULTRASOUND ELASTOGRAPHY, BASKETBALL PLAYERS, MUSCLE-STIFFNESS, DIFFERENT SPORTS, REGIONAL STRAIN, TENDINOPATHY, MOTION, Achilles Tendon, Adult, Age Factors, Aged, Aged, 80 and over, Female, Humans, Knee, Male, Middle Aged, Movement, Patellar Ligament, Quadriceps Muscle, Sex Factors, Tendons, Ultrasonography, Young Adult, 0903 Biomedical Engineering, 0913 Mechanical Engineering, 1106 Human Movement and Sports Sciences, Biomedical Engineering, 4003 Biomedical engineering, 4207 Sports science and exercise

Abstract:

There is increasing evidence that tendons are heterogeneous and take advantage of structural mechanisms to enhance performance and reduce injury. Fascicle-sliding, for example, is used by energy-storing tendons to enable them to undergo large extensions while protecting the fascicles from damage. Reductions in fascicle-sliding capacity may thus predispose certain populations to tendinopathy. Evidence from the Achilles tendon of significant superficial-to-deep non-uniformity that is reduced with age supports this theory. Similar patellar tendon non-uniformity has been observed, but the effects of age and sex have yet to be assessed. Healthy adults (n = 50, 25M/25F) from a broad range of ages (23-80) were recruited and non-uniformity was quantified using ultrasound speckle-tracking during passive knee extension. Significant superficial-to-deep non-uniformity and proximal/distal variations were observed. No effect of age was found, but males exhibited significantly greater non-uniformity than females (p < 0.05). The results contrast with previous findings in the Achilles tendon; in this study, tendons and tendon regions at high risk for tendinopathy (i.e. males and proximal regions, respectively) exhibited greater non-uniformity, whereas high-risk Achilles tendons (i.e. older adults) previously showed reduced non-uniformity. This suggests that non-uniformity may be dominated by factors other than fascicle-sliding. Anatomically, the varied proximal attachment of the patellar tendon may influence non-uniformity, with quadriceps passive resistance limiting superficial tendon movement, thus linking flexibility, non-uniformity and injury risk. This study also provides evidence of a differential effect of aging on the patellar tendon compared with evidence from prior studies on other tendons necessitating further study to elucidate links between non-uniformity and injury.