Quantitative Assessment of Knee Pain and Proprioception in Tibial Rotation in Individuals With Knee Osteoarthritis.

Patients with knee osteoarthritis (OA) exhibit reduced tibial rotations, possibly as a compensatory adaptation to mitigate mechanical stimuli on surrounding tissues. Hence, the passive threshold angle at which knee pain is sensed may reflect that surrounding tissues have received mechanical stimuli sufficient to exceed the nociceptive threshold. This study aimed to measure knee pain and proprioception during tibial rotation quantitatively. Twelve patients with symptomatic medial knee OA and 12 age- and sex-matched controls were included. For patients with knee OA, knee pain was quantified using the pain threshold angle (PTA), at which pain was first perceived during robot-controlled tibial internal rotation (IR) and external rotation (ER) at 0.5°/sec. Knee Injury and Osteoarthritis Outcome Score (KOOS) and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) were also collected. Knee proprioception was measured as the threshold of passive movement detection (TPMD), at which participants first perceived the motion. Pearson's correlations were performed to assess relationships between KOOS/WOMAC and PTA. Independent t-tests compared TPMD between OA and control groups, while paired t-tests compared PTA and TPMD between IR and ER. In knee OA patients, smaller PTA in IR was correlated with worsened scores on KOOS/WOMAC (r = 0.59-0.70; p < 0.05); and PTA in IR was lower than in ER (p = 0.009), indicating increased pain sensitivity in IR. Patients with medial knee OA exhibited impaired proprioception, with a larger TPMD in tibial ER than controls (p = 0.019). This study presents a novel method for quantifying knee pain and proprioception, potentially enhancing the precision of knee OA rehabilitation.