Poster P16 - Assessment of knee pain and proprioception in tibial rotation for knee osteoarthritis

Introduction: Osteoarthritis (OA) is a leading cause of chronic symptoms/disability in the aging population. This disease is believed to originate from local mechanical damages. Altered rotational alignment of the lower limb has been proposed as an etiological factor for knee OA. Impaired knee proprioception in the transverse plane motion may cause knee instability and compromised neuromuscular knee control, thus inducing excessive mechanical loading and symptoms at the knee joint. In addition, patients with knee OA commonly reported increased knee symptoms during weight-bearing activities that require knee twisting. Hence, objective quantification of knee pain and proprioception during transverse plane motion would be important for pain management. However, to the best of our knowledge, knee pain and proprioception in the transverse plane motion have not been objectively measured for patients with knee OA. The aims of the present study were: (i) to measure and compare the knee proprioception during tibial rotation among knee OA, and older and younger healthy adults; (ii) to measure and compare the knee pain/discomfort during tibial rotation among knee OA, healthy older adults, and younger adults; (iii) to explore the difference in proprioception and pain measurements between internal and external rotations. We hypothesized that patients with knee OA have poorer proprioception and lower pain threshold compared with healthy older/younger adults.

Materials and

Methods: Participants: 10 patients with knee OA; 10 age-sex-matched healthy older, and 10 healthy younger (18-40 yrs) adults. Seated at 90° knee flexion, the footplate was rotated in tibial rotation by the off-axis stepping system with a compact 6 degree-of-freedom goniometer attached to the knee. Proprioception

Assessment: Starting from neutral, the knee was passively rotated in internal or external rotation with the footplate rotated at 0.5°/sec. The participant was instructed to close eyes and relax. When he/she sensed the knee motion, pressed a handheld switch and reported the rotation direction. Each participant completed 3 internal and 3 external rotation trials without feeling pain/discomfort. Proprioception was measured by the angle sensed, greater angle indicating worse proprioception. Pain

Assessment: Starting neutrally, the knee was passively pivoted into either internal/external rotation (0.5°/sec). Participants pressed the handheld switch when first felt knee pain/discomfort, then the motor would stop and return to neutral. Each participant completed 3 internal and 3 external rotation trials within their discomfort limits. Pain/discomfort threshold was quantified by the rotation angle where the pain/discomfort was first felt. For proprioception/pain in each direction, we recorded the tibial rotation angle and corresponding rotation of the footplate. Statistical Analysis: One-way ANOVA was used to examine the difference in proprioception/pain across knee OA, healthy older, and younger adults. If significant interaction was found, post-hoc analyses with Bonferroni corrections were conducted. Paired T-test was used to compare proprioception/pain between internal and external rotations. Significance level was 0.05.

Results, Conclusions, and Discussions: Results
We found significant differences in knee pain/discomfort across knee OA, healthy older, and healthy younger adults in tibial internal (F = 7.7, P = 0.002, Fig. 1A) and external (F = 19.2, P < 0.001, Fig .1B) rotations. Post-hoc analyses showed that during either tibial internal or external rotation, knee OA patients had significantly lower pain threshold than healthy older (internal: P = 0.003; external: P < 0.001) and younger (internal: P = 0.024; external: P < 0.001) adults. Knee proprioception was significantly different among knee OA, healthy older, and healthy younger adults in internal (F = 4.7, P = 0.018, Fig. 1C) and external (F = 4.8, P = 0.016, Fig. 1D) rotations, with patients with knee OA had poorer proprioception in internal (P = 0.014) and external (P = 0.016) rotations. We also found knee pain/discomfort threshold was lower in internal rotation than that in external rotation in knee OA, healthy older, and healthy younger adults (all P < 0.05, Fig. 2).

Conclusions
Our findings suggest that individuals with knee OA have poorer proprioception and lower pain threshold in tibial rotational movements. Knee symptoms may be more sensitive during tibial internal rotation.

Discussions
We introduced a novel method to measure knee pain in tibial rotation in the transverse plane, which provided objective and quantitative pain measurement. Our findings indicate that patients with knee OA may have impaired proprioception in the transverse plane movement. We also found that knee pain was more sensitive during internal rotation than external rotation. To our knowledge, this is the first study to examine knee pain and proprioception in tibial rotational movements in knee OA patients. During weight-bearing activities, foot progression angle (toe-in/out) would affect the rotational alignment of the lower-limb kinetic chain, causing re-distribution of the knee impact loading. Hence, gait retraining by modifying foot progression angle can be used as a useful approach to reduce knee joint loading and alleviate symptoms of knee OA. Our work may promote individualized and precise rehabilitation, by determining the specific direction and optimal magnitude of foot progression angle to be modified for better outcomes.

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