Tibiofemoral contact forces and muscle demands in knee osteoarthritis patients during the stand-to-sit and sit-to-stand tasks.

Abstract

Sitting down and standing up are some of the most important functional activities, and frequently, these tasks are affected in patients with knee osteoarthritis (OA). This study compared the muscle and vertical knee contact forces (KCF) differences in patients with knee OA and controls (CTRL) during sit-to-stand and stand-to-sit tasks. Twelve severe unilateral knee OA and eleven CTRL were analyzed. A musculoskeletal modeling approach was used to analyze vertical tibiofemoral forces (total, and in medial and lateral compartments). Joint moments, muscle forces and KCF were compared between the groups, and between affected and contralateral sides. For the stand-to-sit task, the vasti muscles showed lower forces in OA group compared to CTRL. For vastus lateralis, the OA group showed approximately 20% lower peak force. For sitting and standing, the OA group exhibited lower tibiofemoral forces in total and in the medial compartment. When comparing the sides, the OA group showed 40% reduction in peak force in the medial compartment on the affected side for stand-to-sit compared to the contralateral side. For sit-to-stand, the peak force was 22% lower on the affected side in the OA group. The main outcomes suggest a movement strategy to reduce the medial load, frequently the compartment most affected in knee OA patients. The OA group exhibited reduced force in vasti medialis, lateralis and intermedius during stand-to-sit, indicating a deficit in their ability to recruit these muscles eccentrically. Lastly, the contralateral knee experienced increased load during both tasks.