JOA - 2026-04-24 - Journal Article
Divergent Dynamics: Unicompartmental Knee Arthroplasty Enables Greater Propulsive Joint Moments Compared To Total Knee Arthroplasty.
Kuntze G, Korley R, Abelseth G, Ronsky J, Johnston K
Topics
Key Takeaway
UKA produced significantly greater improvements in sagittal hip (β=0.11 Nm/kg·height), knee (β=0.05), and ankle moments and smaller coronal knee moment changes (β=-0.12) than TKA at one year, despite equivalent PROM improvement.
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Summary
This RCT compared instrumented gait analysis outcomes between UKA and TKA patients at one year, measuring changes in peak sagittal and coronal joint moments during push-off alongside OKS and WOMAC scores. UKA patients demonstrated significantly greater increases in propulsive sagittal hip, knee, and ankle moments and significantly smaller increases in coronal knee moments compared to TKA. Despite these biomechanical differences, OKS and WOMAC improved equivalently in both groups, underscoring the insensitivity of PROMs to functional gait restoration.
Key Limitation
The biomechanical cohort of n=28 with only 11 UKA patients is critically underpowered, and the imbalanced group sizes raise concerns about allocation and attrition that could confound the between-group moment comparisons.
Original Abstract
BACKGROUND
Current evidence indicates better functional performance following unicompartmental (UKA) compared to total knee arthroplasty (TKA). This randomized controlled trial addressed continuing knowledge gaps of the differential effects of UKA and TKA on functional joint mechanics and patient-reported outcome measures (PROMs).
METHODS
A total of 38 patients were recruited, and joint moments data were available for 28 patients [UKA n = 11, median age 61 years (range, 45 to 75), women n = 6; TKA n = 17, age 66 years (51 to 77), women n = 9]. Patients were allocated to either UKA or TKA study arms. Instrumented gait analysis was performed before and one year after surgery. Dependent variables were patient-specific changes (follow-up - baseline) in peak sagittal ankle, knee, and hip moments during push-off and maximum coronal knee and hip moments. Patients completed the Oxford Knee Score (OKS) and Western Ontario & McMaster University Arthritis Index (WOMAC) before and six weeks, three months, and one year after surgery. Statistical analyses were conducted using linear mixed effects models for biomechanics and PROMs data.
RESULTS
Unicompartmental knee arthroplasty patients displayed significantly larger increases in sagittal hip (β = 0.11 Nm/kg·height; 95% confidence interval (CI), 0.04 to 0.18; P = 0.003), knee (β = 0.05; 95% CI, 0.01 to 0.09; P = 0.010), and ankle (β = -0.13; 95% CI, -0.25 to -0.01; P = 0.042) moments postoperatively compared to TKA patients. Further, UKA patients displayed significantly smaller changes in coronal knee moments (β = -0.12; 95% CI -0.19 to -0.06; P = 0.001) than TKA patients. While surgical technique did not affect PROMs responses, both UKA and TKA patients reported significant improvements in PROMs scores (P ≤ 0.001) across all follow-up time points.
CONCLUSION
Unicompartmental knee arthroplasty patients demonstrated greater restoration of propulsive gait mechanics and smaller coronal knee moment changes than TKA. In contrast, PROMs improved similarly following both procedures. These findings highlight the value of biomechanical assessment in complementing PROMs and provide clinically relevant context for implant choice and rehabilitation planning in appropriately selected patients following knee arthroplasty.