Hindfoot Alignment Changes One Year After Total Knee Arthroplasty
Overview
This study evaluated hindfoot alignment changes at 1 year post-total knee arthroplasty (TKA) in patients with varus knee osteoarthritis. Results showed significant improvement in hindfoot valgus alignment but no significant change in hindfoot varus alignment over the 1-year period. These findings suggest differential hindfoot adaptation following TKA depending on preoperative hindfoot alignment.
Background
Osteoarthritis of the knee often causes varus or valgus deformities, which affect coronal plane alignment and induce compensatory changes in the subtalar joint. Total knee arthroplasty aims to correct lower limb alignment primarily at the knee, but adjacent hindfoot alignment may also be affected. Previous studies assessed hindfoot alignment changes only up to 3 weeks post-TKA, leaving longer-term effects unclear. Understanding these changes is clinically relevant due to reports of new hindfoot pain developing after TKA, potentially related to postoperative hindfoot alignment.
Data Highlights
Group
Timepoint
Mean VVA (°) ± SD
Mean FTA (°) ± SD
Hindfoot Valgus (n=51 legs)
Pre-TKA
78.4 ± 2.3
184.5 ± 3.1
Hindfoot Valgus
3 weeks post-TKA
76.9 ± 2.1
174.2 ± 2.8
Hindfoot Valgus
1 year post-TKA
75.8 ± 2.0
Not reported
Hindfoot Varus (n=22 legs)
Pre-TKA
73.1 ± 1.8
183.9 ± 3.5
Hindfoot Varus
3 weeks post-TKA
73.3 ± 1.9
174.0 ± 3.0
Hindfoot Varus
1 year post-TKA
73.0 ± 1.7
Not reported
Key Findings
Significant reduction in femorotibial angle (FTA) was observed 3 weeks after TKA in both hindfoot valgus and varus groups, indicating effective correction of knee alignment.
In the hindfoot valgus group, the varus–valgus angle (VVA) significantly decreased progressively from pre-TKA to 3 weeks and further at 1 year post-TKA, indicating improvement in hindfoot valgus alignment.
No significant changes in VVA were observed in the hindfoot varus group at either 3 weeks or 1 year post-TKA, suggesting limited hindfoot varus correction.
The study used a novel radiographic method to measure hindfoot alignment with a threshold VVA of 76.0° to distinguish varus from valgus alignment based on Asian population norms.
Postoperative hindfoot alignment changes may be related to load and dynamic movement over time, explaining the delayed improvement seen at 1 year in the valgus group.
Clinical Implications
Clinicians should be aware that while TKA effectively corrects knee alignment and improves hindfoot valgus deformities over time, hindfoot varus deformities may persist postoperatively. Monitoring hindfoot alignment and symptoms for at least 1 year after TKA is advisable, especially in patients with preoperative hindfoot varus, to manage potential hindfoot pain. Tailored postoperative rehabilitation or orthotic interventions may be necessary to address persistent hindfoot varus.
Conclusion
One year after TKA, patients with preoperative hindfoot valgus showed significant improvement in hindfoot alignment, whereas those with hindfoot varus did not demonstrate significant changes. These findings highlight the importance of considering hindfoot alignment in the comprehensive management of knee osteoarthritis patients undergoing TKA.
References
Kawahara et al. 2024 -- Hindfoot Alignment Assessment One Year Post Total Knee Arthroplasty
