# Preserving Patient‐Specific Knee Motion: A Randomized Clinical Trial of Unicompartmental and Total Knee Arthroplasty

## TL;DR

This study found that unicompartmental knee replacement better preserves natural knee movement compared to total knee replacement, despite similar patient-reported outcomes.

## Contribution

The study provides new evidence that unicompartmental knee arthroplasty preserves native knee kinematics more effectively than total knee arthroplasty.

## Key findings

- Both unicompartmental and total knee arthroplasty improved patient-reported outcomes significantly after surgery.
- Unicompartmental knee arthroplasty showed greater preservation of sagittal plane knee motion and lower coronal plane errors compared to total knee arthroplasty.
- The results suggest that unicompartmental knee arthroplasty may be preferable for patients where preserving natural knee kinematics is a priority.

## Abstract

Unicompartmental knee arthroplasty (UKA) may enable improved functional outcomes compared to total knee arthroplasty (TKA). This randomized controlled trial assessed pre‐ and postoperative patient reported outcome measures (PROMs) and knee joint gait biomechanics for UKA and TKA patients. Patients were allocated to UKA (Oxford Partial Knee, Biomet, USA) and TKA (Persona CR Knee System, Zimmer, USA) study arms. Patients completed the Oxford Knee Score (OKS) and Western Ontario & McMaster University Arthritis Index (WOMAC), as well as instrumented gait analysis before and 1‐year after surgery. Measures of interest: OKS scores; WOMAC sub‐scores; Patient‐specific correlations and root mean squared errors (RMSE) of stance phase sagittal and coronal knee angles. Statistical analysis included linear mixed‐effects models (PROMs; α = 0.0125) and multivariate analysis of variance (gait biomechanics; α = 0.05). A total of 38 patients were recruited (UKA n = 17; TKA n = 21). All PROMs improved significantly following surgery (n = 37, p < 0.001), regardless of surgical technique. A significant effect of surgical technique on gait biomechanics was observed (n = 30, F
4,25, p = 0.010), where UKA patients displayed greater sagittal plane correlations [median(Q1,Q3) UKA 0.985 (0.967, 0.991), TKA 0.955 (0.942, 0.973)]; p = 0.018] and lower coronal plane RMSEs [UKA 3.6 (2.4,5.0)°, TKA 8.6 (5.1, 11.5)°; p = 0.002]. Although patient‐reported outcomes improved similarly following UKA and TKA, UKA more closely preserved native knee kinematics as indicated by the greater similarity of sagittal gait patterns shapes and lower magnitude of coronal angle changes.

Greater preservation of patient‐specific knee kinematics with UKA supports its use in appropriately selected patients and informs the design of targeted, functionally oriented rehabilitation protocols.