Investigation of the relationship between patellar tendon mechanical properties with clinical functional tests, strength values, and pain - cross-sectional study

Objective: We aimed to examine the relationship of ultrasound gray-scale imaging and shear-wave elastography (SWE) with clinical tests, strength measurements, and pain by determining the different tendon features due to patellar tendinopathy in volleyball and basketball players with and without patellar tendinopathy. Materials and Methods: Sixty-three female athletes (mean age 21.86 ± 4.46) between 17-35 ages who played in professional volleyball and basketball leagues were included in the study. After taking clinical history for patellar tendinopathy from all athletes, the athletes filled VISA-P (Victorian Institute of Sport Assessment-Patellar Tendinopathy) questionnaire, and then the clinician examines the athletes' knee. Morphological evaluation and mechanical properties of the patellar tendon were performed by gray scale ultrasound and ultrasound shear-wave elastography. All measurements were taken from both knees at two different knee angles, 0 and 30 degrees. Isometric force measurements were made with an isokinetic dynamometer at the same knee angles. On another day, the counter-movement jump height and the amount of pain occurring in the single-leg decline squat test were evaluated. Results: We found that stiffness increases for both knees at 30 degrees (p= 0.0001 / 0.004) when comparing the two groups. We observed that the stiffness in the right knee increases (p= 0.037) but remained similar for the left knee (p= 0.13) at 0 degrees. On the other hand, a weak negative correlation was found between the thickness and SWE values and the VISA-P score at 0 degrees, especially in the measurements taken from the proximal of the tendon (rho= -0.18), while a weak positive correlation was found with the intensity of pain during decline squat (rho= 0.18). There was a weak correlation between thickness and SWE and VISA-P at 30 degrees (rho= -0.19 / -0.20); besides, it was shown that there was a fair positive correlation between VAS and SWE during one leg decline squat (rho= 0.32). In the measurements taken from other parts of the tendon, no positive or negative correlation was found (rho = 0.01-0.15). When the relationship with the isometric force and jump test was examined, there was only a fair positive correlation between the thickness of the proximal part of the tendon and the isometric force measurements taken at 0 degrees (rho = 0.34). At 30 degrees, this relationship was found to be weak (rho = 0.19). Conclusion: The fact that thickness and shear-wave elastography examinations obtained from the proximal part of the patellar tendon are significantly correlated with clinical tests and differ between athletes with patellar tendinopathy and those without, indicating that SWE can be used as a diagnostic and prognostic monitoring tool in athletes with patellar tendinopathy. Key words: Shear-wave elastography, patellar tendinopathy, ultrasound, isometric strength