Patellofemoral outcomes after kinematic versus mechanical alignment in primary total knee arthroplasty : a focused scoping review of head-to-head comparative studies.

Abstract

Aims: Concerns persist that kinematic alignment (KA) in primary total knee arthroplasty (TKA) may adversely affect the patellofemoral (PF) joint, because most contemporary components were developed under mechanical alignment (MA) principles. This focused scoping review mapped head-to-head comparative clinical evidence on PF outcomes after KA versus MA TKA, and identified key evidence gaps relevant to clinical decision-making.

Methods: A focused scoping review was conducted. PubMed/MEDLINE, the Cochrane Library, and CINAHL were searched from inception to 15 January 2026. We included head-to-head comparative studies directly comparing KA and MA in primary TKA that reported at least one PF-related outcome. PF outcomes were mapped into three domains: 1) PF symptoms and PF-specific patient-reported outcome measures (PROMs); 2) PF-related interventions and complications; and 3) PF imaging/radiological measures. Findings were synthesized descriptively.

Results: A total of 12 studies met the inclusion criteria. Domain A was addressed by only one study and was insufficient for definitive conclusions. Domain B was addressed by six studies; no consistent signal of higher PF-related interventions/complications with KA was identified, and several studies reported numerically fewer PF-related procedures with KA, including lateral retinacular release. Domain C was addressed by ten studies and showed heterogeneous imaging findings; when PF radiological differences were observed, they were not consistently accompanied by worse symptoms or higher PF-related intervention rates. Postoperative rotational alignment was inconsistently assessed.

Conclusion: Current head-to-head comparative evidence is insufficient to determine the definitive PF-specific clinical impact of KA versus MA, mainly because PF-specific PROMs are rarely reported. Although no consistent harm signal was identified, this should not be interpreted as evidence of equivalence. This review primarily defines current evidence gaps, including the need for prespecified PF-specific PROMs, systematic rotational verification, consistent reporting of PF-related interventions/complications, and longer follow-up.