An evaluation of the influence of force- and weight bearing (a)symmetry on patient reported outcomes after total knee arthroplasty.

It has been reported that balance impairments and asymmetrical movement patterns occur in patients after total kne arthroplasty (TKA). The purpose of this study was to evaluate if force- and weight-bearing asymmetry correlate with patient-reported outcomes (PROMs). Twenty patients were prospectively analysed up to 6 months after TKA. Quadriceps- and hamstring force were measured using a hand-held dynamometer. Vertical ground reaction forces during sit-to-stand, stair descending and squatting were assessed by force plates. Patients were asked to complete the KOOS, OKS and 2011 KSS. The symmetry-ratios during sit-to-stand, squat and stair-descent improved significantly. Preopera-tive quadriceps-force was positively correlated with KOOS-Symptoms (r=0.583, p=0.037). The pre-operative load-symmetry ratio during STS was negatively correlated with improvement in KOOS Pain (r=-0.675, p=0.011) and Symptoms (r=-0.674, p=0.008). In deep flexion, preoperative bodyweight ratio was positively correlated with postoperative OKS (r=0.601, p=0.039), KSS-Satisfaction (r=0.675, p=0.011) and improvement in KSS-Satisfaction (r=0.684, p=0.029). Weight bearing and force asymmetry do exist before TKA and take up to at least 6-months to fully recover. The more symmetry in muscle-force and weight-bearing is found preoperatively, the better the PROMs will be at 6 months after surgery.