SYMMETRY OF HIP, KNEE AND ANKLE JOINT POWER DURING CYCLING WITH AND WITHOUT PAIN FROM KNEE OSTEOARTHRITIS

Abstract

Knee osteoarthritis (OA) is one of the most common chronic conditions in Canada (Bombardier et al., 2011). Commonly, the pain caused by knee OA is unequal between knees, which can lead to asymmetry of movement and joint power in daily activities. With hip and knee extensors generating the greatest proportion of power during cycling, it is unclear how the body will compensate if there is a painful knee (Elmer et al., 2011). The purpose of this study was to investigate if seat height, workload and, any difference in knee pain, affected asymmetry of power between hips, knees and ankles during cycling. Asymmetry was defined as the difference between the dominant versus non-dominant leg. It was hypothesized that bilateral joint power would become more symmetrical as seat height increased, workload decreased and any difference in knee pain decreased.

Twenty-six participants aged 45-75 years, with and without knee OA completed six cycling bouts at three seat heights (20°, 30°, 40° minimum knee flexion angle) and two workloads (40W and 75W) on a commercial fit-bike (Pro 1, Purely Custom, USA). Self-reported knee pain on the Numeric Pain Rating Scale (NPRS) was recorded for each knee before the first bout and after each bout. Three-dimensional kinematics were collected with a commercial motion capture system (Optotrak Certus, NDI, Canada) and synchronized three-dimensional kinetics were collected with commercial instrumented 3-axis pedals (Science to Practice, Slovenia). Joint angles and power were calculated in Visual3D (HAS-Motion, Germantown, USA) for the full bout. From that full bout, a one-minute portion was selected. Then revolutions in that one-minute were averaged to one pedal cycle using custom Python code.

Seat height and workload did not have a significant effect on symmetry of joint power. A significant relationship was found between hip, knee and ankle joint power difference and knee pain difference. The leg with the more painful knee produced less power than the opposite leg (p < 0.001, both workloads). Evaluating asymmetry for each joint revealed an interesting pattern. The more painful knee produced more joint power than the less painful knee (p = 0.003, 75W workload). The hip and ankle in the leg with the more painful knee produced less power than the contralateral joints (p < 0.001, both workloads). These results demonstrated the relationship between lower limb joint power and knee pain during cycling and in turn, how these joints could contribute power in the presence of knee pain. These findings are also relevant to rehabilitation clinicians, because they show rehabilitation could aim to boost the power produced by healthy joints to offload a symptomatic joint.