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

Purpose: 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. Methods: 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. Results: 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. Conclusion: 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 of Evidence: Level III.