Variable compensation during the sit-to-stand task among individuals with severe knee osteoarthritis.

Background: Individuals with knee osteoarthritis (OA) show variability during the sit-to-stand (STS) task, so they may not perform the STS in the same way. This study aimed to determine whether individuals with knee OA have different strategies in performing the STS.

Methods: Participants with knee OA and able-bodied individuals underwent STS evaluation at a self-selected pace with use of a motion measurement system consisting of 12 cameras and 2 force plates.

Results: In total, 101 participants (57 women) with knee OA showed 3 main STS strategies. As compared with the 27 controls (14 women), 24 OA participants, compensated STS, showed greater trunk flexion (47.1° vs. 38.3°; P<0.01) and trunk obliquity (4.6° vs. -0.8°; P<0.001) when completing the STS task in the same amount of time as controls (2.4 vs. 2.7s; P=0.999). The second group (n=59), inadequately compensated STS, also compensated with trunk flexion (47.7° vs. 38.3°; P<0.01) and trunk obliquity (1.6° vs. -0.8°; P<0.001) but took longer than controls (3.4 vs. 2.7s; P=0.001). The third group (n=18), severe impaired STS, took an extended amount of time to execute the STS (6s), with marked trunk flexion (59.2°) and obliquity (4.1°), so participants in this group were perhaps severely impaired in completing the STS.

Conclusion: This study identified 3 groups STS trunk strategies among participants with STS. Moreover, the data reveal a concise representation of the relations among strategy variables. The findings could be used to simplify the characterization of the STS among patients with knee OA and aid with follow-up.