# Preserving joint line orientation in TKA improves short‐ to mid‐term outcomes: A systematic review and meta‐analysis

## TL;DR

Preserving the joint line orientation during knee replacement surgery improves patient outcomes in the short to mid-term.

## Contribution

This study shows that aligning TKA with individual knee anatomy improves functional outcomes compared to standard approaches.

## Key findings

- Joint line preserving techniques improved patient-reported outcome measures like FJS and KOOS.
- Subgroup analyses confirmed benefits in low-risk studies, supporting the effectiveness of JLP approaches.
- Results suggest personalized surgical strategies based on knee phenotype may optimize TKA outcomes.

## Abstract

Joint line orientation (JLO) has been identified as a potential factor influencing clinical outcomes following total knee arthroplasty (TKA). This systematic review and meta‐analysis aimed to assess whether preserving the JLO according to the individual knee phenotype is associated with improved clinical and functional outcomes. We hypothesised that joint line preserving (JLP) techniques would result in superior patient‐reported outcome measures (PROMs) and better functional performance compared to non–joint line preserving (nJLP) approaches.

A systematic search of Pubmed, CENTRAL, and Web of Science was conducted to identify comparative studies evaluating JLP versus nJLP in TKA. Studies reporting PROMs and other clinical indicators with a minimum follow‐up of 12 months were included. Risk of bias was assessed using the RoB 2 tool for randomised trials and the ROBINS‐I tool for non‐randomised studies. Meta‐analyses were performed for PROMs and range of motion, with subgroup analyses based on study quality.

Forty‐three studies were included in the qualitative analysis, and 38 in the meta‐analysis. The Forgotten Joint Score (MD: 7.59), Knee Function – Knee Society Score 2011 (MD: 6.48), Knee Injury and Osteoarthritis Outcome Score (MD: 2.74) and Oxford Knee Score (MD: 1.02) all showed statistically significant differences favouring JLP. Most subgroup analysis of low and low‐to‐moderate risk of bias studies further supported these effects.

Joint line preservation in TKA is associated with short‐ to mid‐term improvements in PROMs and other clinical outcomes. While the effect may vary across patient populations, these findings support the relevance of JLO in optimising functional results. A more comprehensive and standardised phenotypic approach could be key to better identifying the subgroups that benefit most from this strategy.

Level III.

This systematic review and meta‐analysis found that preserving joint line orientation in total knee arthroplasty improves short‐ to mid‐term outcomes. Joint line–preserving techniques significantly enhanced PROMs like FJS, KOOS, OKS and Knee Society scores. Results suggest that aligning TKA to individual knee phenotypes may optimise function, supporting more personalised, phenotype‐based surgical strategies.