Background
Osgood-Schlatter Disease (OSD) impacts millions of young athletes every year, yet its biomechanical etiology remains unclear. It’s been postulated that increased growth velocity in children elevates tension within the patellar tendon, placing distal strain on the tibial tubercle, causing anterior knee pain, but this process has not been previously elucidated. The purpose of this study was to evaluate axial tensile and transverse compressive strains in adolescent patellar tendons during exercise to identify differences between those with and without OSD using a cumulative strain, ultrasound elastography measurement method [REF: Chimenti et al 2016].
Methods
Axial tensile and transverse compressive strains of the patellar tendon in eight adolescents with OSD and ten adolescents without OSD were quantified from ultrasound elastography images. Multiaxial strains of the patellar tendon were assessed as the participant performed two different exercises: 1) participant seated with leg fully extended, participant bends knee, followed by a return to initial extended position; (2) participant standing performs a squat and then returns to initial standing position. Participants’ disease severity was clinically assessed using the VISA-P and Cincinnati knee scale.
Results
Mean age was 13.1 years (+/- 2.7), 39% were male (63% of OSD group). There was no statistically significant difference in patellar tendon tensile strains during the seated knee flexion and squat positions between groups (p = 0.99, p = 0.83 respectively). The OSD group had significantly less tendon compression compared to the non-OSD group during both the knee flexion (p <0.01), and squat exercises (p <0.05).
Conclusions/Significance
Adolescents with OSD had lower transverse compressive strains in the patellar tendon as compared to adolescents without OSD. In contrast, tensile strains were not increased in children with OSD. These findings appear to contradict the tension hypothesis postulating that OSD is caused by increased patellar tendon axial tension associated with rapid bone growth, Instead, impingement from the tibia leading to transverse tendon compression may lead to an adaptive stiffing the patellar tendon, However, further research is needed to confirm this hypothesis.
While OSD is a common cause of knee pain in growing athletes that frequently leads to loss in participation, its etiology is unclear, making development of effective treatment approaches difficult. This study highlights differences in multiaxial patellar tendon strains in adolescents with OSD which may help direct future research on management strategies.
