Summary

The course of muscle strength recovery for UKA is different to TKA in which UKA patients regained their muscle strength and endurance sooner than TKA patients.

Abstract

Introduction

The recovery of muscle strength has been minimally compared between total (TKA) and medial unicompartmental knee arthroplasty (UKA). A better understanding of the rehabilitation enables surgeons to set realistic patients’ expectations. This study aimed to compare recovery of extension and flexion leg muscle strength and patient-reported outcome measures (PROMs) between TKA and medial UKA.

Methods

A prospective study was performed among 369 patients (mean age: 68.7±7.9 years, 55.3% female) undergoing a TKA or medial UKA for symptomatic osteoarthritis of the knee. Muscle strengths were determined by the peak isokinetic extension- and flexion muscle strengths using a Biodex™. PROMs included the Knee injury and Osteoarthritis Outcome Score-Physical function Short form (KOOS-PS), Oxford Knee Score (OKS), Forgotten Joint Score (FJS) and Numeric Rating Scale for pain (NRS). Recovery over time was explored using longitudinal analysis, and two-sample t-tests were used for comparison of continuous variables.

Results

At six and 12 months postoperatively, UKA patients had significantly greater maximum extension strength in both the operated (six-months: TKA: 73.3±29.5 Nm/kg, UKA 95.3±28.8; p<.001. 12-months: TKA: 87.3±32.9, UKA 110.3±32.6; p<.001) and unaffected knee (six-months: TKA: 102.3±38.3, UKA: 119.2±37.2; p<.001. 12-months: TKA: 108.5±41.5, UKA: 120.7±35.8; p=.013). However, results were statistically insignificant for flexion strength outcomes. No significant differences in speed of recovery were observed. Significantly greater NRS pain, KOOS-PS, OKS and FJS scores were observed at six and 12 months postoperatively favoring medial UKA.

Conclusion

This study demonstrated that the course of regaining muscle strength for UKA is different to TKA in which UKA patients regained their muscle strength and endurance sooner than TKA patients. Additionally, patients who underwent a medial UKA had significantly superior KOOS-PS, OKS, FGS and NRS scores at six and 12 months postoperatively, compared to TKA.