The characteristics of the muscle-tendon unit in children affected by Osgood-Schlatter disease

This study aimed to compare the morphological/mechanical characteristics of muscle-tendon unit (MTU) in children affected by Osgood-Schlatter disease (OSD) and healthy children. The morphological/mechanical properties of MTU were investigated in fifteen subjects (21 legs) who were affected by OSD (OSD group) and 15 subjects (28 legs) found to have no OSD (CON group). Tendon structure stiffness, elongation, and strain of knee extensors were measured using ultrasonography. In addition, we calculated the ratio of fascicle to femur length. Tendon structure stiffness was significantly higher in the OSD group than in the CON group (P = 0.0008). Maximum elongation (P = 0.0006) and maximum strain (P = 0.0003) were significantly lower in the OSD group than in the CON group. There was no significant difference in the MVC values of the knee extensors between the two groups (P > 0.05), nor was there a significant difference in the ratio of fascicle to femur length between the two groups (P > 0.05). These results indicate that mechanical properties of tendon structure are related to the presence of OSD and that an imbalance in the morphological development of muscles and bones has little association with the presence of OSD.