Prospective observational study of coronal and sagittal alignment after primary total knee arthroplasty and their association with early (3-month) functional outcomes.

INTRODUCTION

Total knee arthroplasty (TKA) is a widely accepted procedure for managing end-stage osteoarthritis. Optimal component alignment, particularly in the coronal and sagittal planes, is believed to influence postoperative function and implant longevity. This study prospectively evaluates the relationship between alignment parameters and early functional outcomes following primary TKA.

METHODS

A prospective observational study was conducted in 100 patients undergoing unilateral primary TKA for osteoarthritis. Coronal alignment (HKA) was measured on preoperative and 6-week postoperative long-leg radiographs, and sagittal parameters (posterior tibial slope and femoral component flexion angle) were measured on 6-week lateral radiographs. Functional outcomes (KSS and WOMAC) were recorded at baseline and 3 months, and analyses were performed using baseline-to-3-month change scores. Associations between alignment parameters and functional improvement were explored using correlation analyses.

RESULTS

Significant improvements were observed in both Knee Society Score (KSS) and WOMAC outcomes at three months following TKA. Mean KSS knee scores improved from 49.55 ± 9.9 preoperatively to 85.30 ± 7.6 at three months, while KSS functional scores increased from 39.72 ± 11.8 to 78.00 ± 6.3 (both p < 0.001). Mean WOMAC total scores decreased from 65.2 ± 8.7 preoperatively to 18.6 ± 6.4 at 3 months (p < 0.001). Correlation analysis demonstrated a moderate negative association between postoperative coronal alignment deviation and improvement in both KSS knee (r = − 0.27, p = 0.006) and functional scores (r = − 0.29, p = 0.004), as well as WOMAC improvement (r = − 0.28, p = 0.005). Among sagittal plane parameters, posterior tibial slope showed a weak positive correlation with improvement in KSS functional score (r = 0.24, p = 0.010), whereas femoral component flexion angle did not demonstrate a significant association with functional or WOMAC outcomes.

CONCLUSION

Coronal alignment deviation from neutral was modestly associated with smaller early functional gains after TKA, while sagittal parameters showed weaker and less consistent relationships. Alignment appears to be one of several contributors to early recovery.