JOA - 2026-04-16 - Journal Article
Pre- and Postoperative Alignment of the Knee Impacts Ankle Alignment: Analysis of 4,698 Total Knee Arthroplasties.
Spadini M, Same K, Simon S, Huber S, Lari Y, Hofstaetter JG
Topics
Key Takeaway
In 4,698 TKAs, preoperative HKA strongly predicted postoperative GP and GT ankle alignment angles (P<0.001), and residual ankle alignment differences persisted even when neutral postoperative HKA was achieved.
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Summary
This retrospective single-center study examined whether pre- and postoperative knee alignment (HKA) influences ankle alignment using long-leg radiographs in 4,698 mechanical alignment TKAs. Ground-to-tibial plafond (GP) and ground-to-talar dome (GT) angles correlated strongly with preoperative HKA across all varus/valgus subgroups (P<0.001), and preoperative HKA remained a significant predictor of postoperative ankle alignment even after achieving neutral HKA. Talar tilt was unaffected by HKA, suggesting GP and GT changes reflect coordinated en-bloc distal ankle adaptation rather than intrinsic ankle joint deformity.
Key Limitation
The study lacks postoperative clinical outcome data and ankle symptom assessment, so the functional and long-term articular consequences of the observed ankle alignment changes remain unknown.
Original Abstract
BACKGROUND
Limited data exist on the effects of total knee arthroplasty (TKA) on ankle alignment. This large-scale study aimed to assess pre- and postoperative ankle alignment in patients undergoing TKA using long-leg radiographs.
METHODS
This retrospective single-center study analyzed 4,698 radiographs from patients undergoing mechanical alignment TKA. Included patients had a median age of 71 years (range, 31.8 to 95.0) and a mean body mass index (BMI) of 29.9. Patients were grouped by pre- and postoperative hip-knee-ankle (HKA) angles. Outcomes were ground-to-tibial plafond (GP), ground-to-talar dome (GT), and talar tilt (TT) angles. Propensity score matching, followed by weighted linear regressions, was used to assess the influence of HKA on ankle angles.
RESULTS
Preoperative angles showed a similar pattern, from 10.8 ± 3.8, 10.1 ± 4.3, and 10.5 ± 5.3 degrees in the severe valgus group to -12.5 ± 2.3, -5.2 ± 3.5, and -5.6 ± 4.3 in the severe varus group for HKA, GP, and GT, respectively. A strong correlation was observed between preoperative HKA and GP and GT across all groups (P < 0.001). Preoperative HKA significantly predicted postoperative GP and GT in most groups (P < 0.001). Among patients who had normal postoperative HKA, those who had preoperative valgus HKA showed higher postoperative GP and GT angles than those who had preoperative varus HKA. Postoperative HKA was also a strong predictor of postoperative GP and GT (P < 0.001). Talar tilt was largely unaffected by HKA, and neither BMI nor age significantly influenced the angles.
CONCLUSIONS
Ankle alignment, defined by GP and GT, is strongly influenced by both pre- and postoperative knee alignment, with preoperative HKA affecting postoperative ankle alignment even when normal postoperative HKA is achieved. The unaffected TT may indicate that alterations in GP and GT represent coordinated shifts of the entire distal ankle.