Assessing neuromuscular control in knee osteoarthritis

Purpose: Individuals with knee osteoarthritis (KOA) exhibit reduced muscles strength and proprioception. The interaction of muscle weakness and proprioception has been suggested to be predictive of functional outcomes in independent cohorts. It is thought that the poor muscle strength and proprioception impairs neuromuscular control which negatively impacts on health outcomes in KOA. The purpose of the study was to assess how biomechanical impairments associated with KOA determine the loss of neuromuscular control and its subsequent impact on health outcomes in KOA. Method(s): Biomechanical impairments of 18 symptomatic KOA participants (62.7 +/- 9.1 yrs; 29.7 +/-5.2 kg/m2) were assessed, including isometric muscle strength of the knee flexors and extensors and passive movement sense (proprioception). Neuromuscular control was determined from submaximal force accuracy and steadiness and muscle coactivation during stair ascent for anterior-posterior and medial-lateral muscles. Knee injury and Osteoarthritis Outcome Score (KOOS) domains where used to assess pain, symptoms, activities of daily living (ADL), sports and recreation and quality of life (QOL). Linear regression was performed to assess if biomechanical impairments predict neuromuscular control and Pearson's correlation were performed to assess the relationship between neuromuscular control and health outcomes. Result(s): Biomechanical impairments (muscle strength and proprioception) significantly predicted loss of neuromuscular control outcome measures: force accuracy (R2 = 0.546, P = 0.01), muscle co-activation both hamstrings - quadriceps (R2 = 0.525, P = 0.013), and vastus lateralis - vastus medialis (R2 = 0.800, P = 0.001), but not force steadiness (R2 = 0.192, P = 0.378). Neuromuscular control measures force accuracy and force steadiness were weakly correlated with all KOOS domains in participants with KOA (r = -0.111 - -0.320; r = 0.122 - -0.178; force accuracy and steadiness respectively). Muscle co-activation, anteriorposterior and medial-lateral was weakly correlated with all KOOS domains for participants with KOA (r = -0.098 - 0.244; r = -0.079 - 0.293; anterior-posterior and medial-lateral respectively). Conclusion(s): Muscle weakness and poor proprioception predict loss of neuromuscular control in participants with KOA. This suggests that both passive and active joint structures may influence neuromuscular control. When looking at the impact loss of neuromuscular control has on the health outcomes of KOA, force accuracy and steadiness measure strongly correlated with health outcomes in control participants, whereby good force accuracy measures predicted good health outcomes, however, this relationship was weak in participants with KOA. The muscle co-activation measures of neuromuscular control showed weak relationship with health outcomes for both KOA and control participants.