Voluntary Quadriceps Activation Deficits in Patients with Tibiofemoral Osteoarthritis: A Meta-Analysis

Abstract

Volitional quadriceps activation deficits have often been associated with tibiofemoral osteoarthritis (TFOA). Although this clinical impairment is commonly hypothesized to be a contributing factor to dysfunction and biomechanical alterations, no reviews have systematically determined the magnitude of quadriceps activation deficits in people with TFOA. PURPOSE: To assess the magnitude of quadriceps activation deficits in the involved and uninvolved extremities of patients with TFOA, as well as healthy matched controls. METHODS: A search was performed using Web of Science from 1970 to September 14, 2009 with the search terms "osteoarthritis" AND "quadriceps activation" OR "quadriceps inhibition" and cross referencing pertinent articles. Fourteen studies written in English, reporting quadriceps activation means and standard deviations in patients with tibiofemoral OA via a method using an exogenous electrical stimulation, were evaluated for methodological quality and included for data analysis. The number of participants and mean activation levels were used to calculate weighted means for the involved limb (14 studies), a subset of the studies reporting both the involved and uninvolved limb (6 studies), and a population of control subjects (6 studies). RESULTS: The weighted grand mean from the 13 studies evaluating volitional quadriceps activation in the involved limb was 80.9% (95% CI 80 to 81.9%), which was slightly lower than the uninvolved limb mean (81.7%; 80.1 to 83.3%). An additional involved mean calculated from only the subset of studies reporting bilateral activation means was the lowest (76.8%; 74.8 to 78.8%), and offered a direct comparison to the samples in the uninvolved limb mean. The volitional quadriceps activation mean from the control group was higher than all other means (89.9%; 88.3 to 91.5%). The mean difference was 10.8% (9.9 to 11.7%) between the involved and control means and 4.9% (3.6 to 6.2%) between the involved and uninvolved means. CONCLUSION: Quadriceps volitional activation was lower in both involved and uninvolved limbs of patients with TFOA and in comparison to healthy controls. This study provides data on the magnitude in which quadriceps activation deficits exist in patients with TFOA, as well as supporting the theory of bilateral neuromuscular effects of joint injury.