Association between pain, muscle strength, balance and joint biomechanics in patients undergoing total knee arthroplasty

Introduction: Knee osteoarthritis (OA) presents a significant clinical problem amongst older adults, as they are affected by knee pain and impaired knee joint function. When conservative treatments options are no longer effective, total knee arthroplasty (TKA) is often considered. However, about 20% of patients report impaired gait function and dissatisfaction after the procedure. The overall goal of this study was to determine the association between patient-reported outcome measures and functional parameters in patients undergoing TKA. The specific aims were to (1) examine differences in the patient-administered instrument “Knee injury and Osteoarthritis Outcome Score” (KOOS) and functional parameters between OA patients and asymptomatic controls and (2) investigate the association between KOOS and functional parameters in OA patients before and after undergoing TKA.
Methods: KOOS, muscle strength, balance, range of motion (ROMSP) of the knee, and moment of the knee during gait were assessed in patients with knee OA scheduled for a TKA (n = 8) before, three months, and 12 months after surgery. Asymptomatic controls (n = 8) were measured for the same parameters as the reference. Differences between OA patients and controls were calculated by applying a t-test for independent samples. Differences between measurements time points in OA patients were calculated by applying a repeated-measures ANOVA. Correlations between KOOS and functional parameters were determined using the Pearson bivariate correlation coefficient.
Results: Patients with knee OA showed lower KOOS scores than asymptomatic controls (Symptoms, Sport, and QOL: p < .01; Pain and ADL: p < .001). OA patients with higher QOL and Sport scores had greater ROMSP. Higher QOL scores were also associated with better balance scores. When OA patients and controls were grouped, subjects with better Symptom, ADL, Sport, and QOL scores had greater ROMSP. Additionally, higher Sport and QOL scores were associated with greater muscle strength. All KOOS subscores improved after undergoing TKA (Symptoms: p < .01; Pain, ADL, Sport, and QOL: p < .001).
Conclusion: The results of this study suggest that KOOS scores are worse in OA patients but improve significantly after TKA. The current findings further indicate that improvements in KOOS scores can be observed right after surgery, whereas improvements in functional parameters are observed later. Hence, rehabilitation programs should also focus on medium-term improvements in function when treating patients after a TKA. Moreover, inconsistent evidence was found that KOOS scores were associated with functional parameters. Further research with a larger sample size examining the reasons for inconsistent findings and a lack of difference in functional parameters is needed.