Aug 4 • Dr. Stephen Howell, MD

The Quadriceps Malalignment Question

No Evidence Supports External Rotation of the Femoral Component in Kinematic Alignment

When a CT scan shows a laterally or externally rotated proximal quadriceps tendon, should the femoral component be externally rotated during kinematic alignment total knee arthroplasty (KA TKA)?

After more than 20 years of clinical experience and published research, the evidence points to a clear answer: No.

In this KA-Optimized Editorial, Dr. Stephen Howell reviews the evidence behind quadriceps malalignment, explains why the recommendation for external rotation originated in patellofemoral arthritic knees and mechanical alignment TKA, and discusses why the data do not support applying that recommendation to kinematic alignment.
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Key Takeaways
  • No evidence supports externally rotating the femoral component in kinematic alignment.
  • Quadriceps malalignment thresholds were established in patellofemoral arthritis and mechanically aligned TKA not in KA TKA.
  • Approximately 3,700 kinematically aligned TKAs performed without external femoral rotation demonstrate a patellofemoral instability rate of just 0.4%.
  • Two independent research groups found no relationship between quadriceps tendon axial angle and outcomes in kinematically aligned knees.
  • When the quadriceps vector is oriented laterally, evidence supports using a 20° valgus prosthetic trochlear groove, not external rotation of the femoral component.
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Bottom Line:

The evidence consistently supports four conclusions:
  • Patellofemoral instability is rare in kinematically aligned TKAs using a 6° valgus trochlear groove.
  • Quadriceps malalignment values were derived from mechanically aligned knees with patellofemoral arthritis and have not been validated in KA TKA.
  • Direct studies in kinematic alignment show no association between quadriceps tendon axial angle and patient outcomes.
  • When the quadriceps vector is truly lateral, the preferred solution is a 20° valgus prosthetic trochlear groove—not external rotation of the femoral component.
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Talbot S, et al. Quadriceps tendon malalignment and LFPFJOA. KSSTA 2023;31:5950–5961.

Talbot S, et al. Preoperative quadriceps malalignment and femoral component ER. KSSTA 2025;33(4):1418–1427.

Razick D, et al. PQT location not associated with KA TKA outcomes. J Exp Orthop 2024;11:e70075.

Akagawa M, et al. No QTAx–PROM association in KA TKA. KSSTA 2026. doi:10.1002/ksa.70310

Nedopil AJ, et al. Patellofemoral instability after KA TKA. Int Orthop 2017;41:283–291.

Klasan A, et al. ANZ registry KA-PSI vs conventional Triathlon. J Arthroplasty 2020;35:2872–2877.

Dossett HG, et al. Long-term RCT of KA vs MA TKA. J Arthroplasty 2023;38(6S):S209–S214.

Howell SM, et al. Switching from 6° to 20° valgus PTG. Arthroplasty Today 2026;37:101930.

Rak D, et al. Setting condyles to restore the medial pre-arthritic surface. KSSTA 2023;31(12):5319.

Howell SM. From My Perspective… The Quadriceps Malalignment Question: no evidence to externally rotate the femoral component in kinematic alignment. J Orthop Exp Innov. In press. Open access.


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