Association among neuromuscular and anatomic measures for patients with knee osteoarthritis

Objective: To investigate neuromuscular and anatomic factors involved in varus gonarthrosis by identifying measures associated with degenerative changes. Design: Descriptive study. Individual measures that explained substantial portions of the variability in ratings of knee joint-degenerative changes in patients with knee medial compartment osteoarthritis. Setting: Outpatient orthopedic clinic and biomechanics and muscular assessment laboratory. Patients: Volunteer sample of 20 subjects (age range, 59 +/- 9 yr) with no history of neurologic disease. Interventions: Not applicable. Main Outcome Measures: We assessed degenerative changes, varus alignment, standing balance, and knee proprioception. Weight-bearing radiographs were used to assess the extent of degenerative changes and the degree of varus alignment. Single-limb standing balance control was assessed through tests performed on a force platform. Knee proprioception was assessed with an isokinetic dynamometer, using a joint angle replication test. Results: Forward-stepwise multiple linear regression indicated that the extent of degenerative changes could be best predicted from a linear combination of the independent variables, varus alignment, and standing balance (R =.80, F-2,F-17 = 14.81, p =.0002). Sixty-four percent of the variability in ratings of degenerative changes was explained by alignment and standing balance measures (37% by varus alignment, 27% by standing balance). Alignment and balance measures were poorly correlated (r =.12, p =.63), further suggesting that they provided different information about gonarthrosis. Conclusions: Although varus alignment is widely accepted as a clinically important factor in gonarthrosis, and is the focus of many treatment efforts, our results suggest that objective measures of standing balance are also important. As a result, the potential impact of rehabilitation to improve the control of standing balance should be further evaluated in this patient population.