The Influence of Radiographic Severity on the Relationship between Muscle Strength and Joint Loading in Obese Knee Osteoarthritis Patients

Objective. To investigate the relationship between knee muscle strength and the external knee adduction moment during walking in obese knee osteoarthritis patients and whether disease severity influences this relationship. Methods. This cross-sectional study included 136 elderly obese (BMI > 30) adults with predominant medial knee osteoarthritis. Muscle strength, standing radiographic severity as measured by the Kellgren and Lawrence scale, and the peak external knee adduction moment were measured at self-selected walking speed. Results. According to radiographic severity, patients were classified as “less severe” (KL 1-2, N = 73) or “severe” (KL 3-4, N = 63). A significant positive association was demonstrated between the peak knee adduction moment and hamstring muscle strength in the whole cohort (P = .047). However, disease severity did not influence the relationship between muscle strength and dynamic medial knee joint loading. Severe patients had higher peak knee adduction moment and more varus malalignment (P < .001). Conclusion. Higher hamstring muscle strength relates to higher estimates of dynamic knee joint loading in the medial compartment. No such relationship existed for quadriceps muscle strength. Although cross sectional, the results suggest that hamstrings function should receive increased attention in future studies and treatments that aim at halting disease progression

THE EFFECTS OF CONSTRAINING OPENSIM INVERSE KINEMATICS TO A BONE PIN MARKER DEFINED RANGE

The aim of this study was to apply bone pin kinematic constraints to an OpenSim model to determine differences in knee joint kinematics and kinetics beween the constrained and unconstrained solutions. In vivo data from healthy, anterior cruciate ligament deficient and reoonstructed patients completing a forward jump lunge were combined with bone pin data from a past study to redefine ranges that the knee degrees of freedom were constrained to. Differences between the constrained and unconstrained solutions existed for all participants at various points of the jump lunge movement, especially at the time of impact. Soft tissue artifact was most apparent in transverse plane translations. In conclusion, musculoskeletal modelling based solely on surface marker positions is inherently affected by soft tissue artifact and thus, results from these analyses should be interpreted with caution

Dynamics of Postural Control in Elite Sport Rifle Shooters

Thirteen shooters and eleven non-shooters completed two-legged and single-legged stance on a force platform. The dynamics of the center of pressure trajectory was assessed using sample entropy, correlation dimension and entropic half-life. Additionally, the body sway was quantified as the elliptical area of the trajectory. The shooters had lower sample entropy and tended to have longer entropic half-life during the single-legged stance. Across the two tasks, the correlation dimension in the anterior-posterior direction and the body sway in both directions were lower in the shooters. This suggests that extensive training in quiet stance is associated with altered postural control, especially during challenging single-legged stance and to a lesser extend during two-legged stance