Background: Osgood-Schlatter disease (OSD) is a sports-related disorder involving apophysitis, which affects the tibial tuberosity. The identification of factors related to OSD is important for its prevention and early recovery from the disease. This study aimed to compare the passive mechanical properties of the muscle-tendon unit in children affected by an OSD and healthy children, by using ultrasound real-time tissue elastography. Methods: Eighteen legs affected by OSD (OSD group) and 42 healthy legs (control: CON group) were assessed. The elasticity was obtained from the quadriceps muscles and patella tendon (PT) using real-time tissue elastography. The strain ratio (SR; muscle or tendon/reference ratio: strain rate of the muscle or tendon divided by that of the reference material) was calculated as an indicator of the elasticity of the tissue of interest. Results: The SR of the PT in the OSD group was significantly lower than that in the CON group (P<0.05). We found no significant difference between the groups in terms of the SR value of all muscles (P>0.05). Conclusions: The results suggest that a PT with a lower SR may be associated with an OSD and that the passive mechanical properties of the quadriceps muscles have limited association with an OSD. Levels of Evidence: Level IV.

No abstract

The aim of the present study was to examine the acute effects of dermal suction on the passive mechanical properties of specific muscles and joints. Dermal suction was applied to the calves of 24 subjects. Passive plantar flexion torque was measured with the right knee fully extended and the right ankle positioned at 20°, 10°, 0°, and −10° angles, where 0° represents the ankle neutral position, and positive values correspond to the plantar flexion angle. The shear wave velocity (SWV) (m/s) of the medial gastrocnemius was measured in the same position using ultrasound shear wave elastography. The relationship between the joint angle and passive torque at each 10° angle was defined as passive joint stiffness (Nm/°). Passive muscle and joint stiffness were measured immediately before and after the dermal suction protocol. When the ankle joint was positioned at 20° (r = 0.53, P = 0.006), 10° (r = 0.43, P = 0.030), and −10° (r = 0.60, P = 0.001), the SWV was significantly higher after dermal suction than that before dermal suction. Regarding joint stiffness, we found no significant difference between the pre- and post-dermal suction values (partial η2 = 0.093, P > 0.05). These findings suggest that dermal suction increases passive muscle stiffness and has a limited impact on passive joint stiffness.

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. K E Y W O R D Ssports injury, stiffness, tibial tuberosity, ultrasound