Alignment strategies in total knee arthroplasty and the patellofemoral joint: A systematic review.
BACKGROUND: Different alignment strategies in total knee arthroplasty (TKA) may affect the patellofemoral joint. Mechanical alignment (MA) is commonly used but may alter native anatomy. Newer strategies such as kinematic alignment (KA), restricted kinematic alignment (rKA), and functional alignment (FA) aim to better restore native joint mechanics. This study provides an overview of the effects of alignment strategies on patellofemoral outcomes after TKA. METHODS: A literature search in July 2025 identified studies comparing patellofemoral outcomes in TKA using different alignment strategies. Of 166 studies screened, eight met inclusion criteria. Three studies were considered medium quality and five studies low quality. RESULTS: KA and rKA more closely restored native trochlear morphology than MA and FA, reducing outliers in the anterior trochlear line compared with MA and FA. MA showed greater trochlear translation, suggesting worse patellar tracking. Trochlear angles were more anatomical in KA and rKA. However, KA was associated with increased internal femoral component rotation and more outliers beyond safe thresholds. FA showed more consistent rotational positioning, generally within safe limits. Lateral patellar shift and intraoperative lateral release rates did not differ significantly between KA and MA. Only one study reported patella-specific clinical outcome scores, finding no difference between FA and adjusted MA. CONCLUSION: KA and rKA better restore trochlear morphology, but risk excessive internal femoral component rotation. FA provides a more balanced approach. MA, while widely used, is linked to altered trochlear shape and worse patellar tracking. The clinical impact of these radiological differences remains unclear, and higher-quality studies are needed.