Unrestricted kinematic alignment offers limited functional benefit over mechanical alignment in medial pivot total knee arthroplasty: A randomized controlled trial using conventional instrumentation.

purposeThe aim of this randomized controlled trial was to compare clinical outcomes between kinematic alignment (KA) and mechanical alignment (MA) in total knee arthroplasty (TKA) using a medial-pivot (MP) prosthesis and conventional instrumentation. The primary hypothesis was that KA would result in improved joint awareness at 2 years postoperatively.

methodsOne hundred patients with end-stage knee osteoarthritis were enroled between October 2020 and December 2024 and randomized to receive either KA or MA. All surgeries were performed by a single surgeon using the same MP prosthesis. Clinical scores (OKS, WOMAC, KSS, FJS-12) and radiographic measurements were collected preoperatively and at a 2-year follow-up. Subgroup analysis was performed based on coronal knee alignment (Coronal Plane Alignment of the Knee classification).

resultsAt 2 years, KA demonstrated statistically significant differences in KSS Pain (p = 0.024), WOMAC total (p = 0.003) and FJS-12 (p = 0.001) compared to MA. The range of motion did not differ significantly between groups (p = 0.201). In subgroup analyses, patients with varus alignment showed a statistically significant and clinically meaningful improvement in WOMAC scores. However, most between-group differences did not exceed established minimal clinically important difference thresholds.

conclusionKA with an MP TKA design was associated with statistically higher functional scores and joint awareness compared to MA, particularly in patients with varus alignment. However, the observed differences were modest, and further studies are warranted to clarify the clinical relevance of KA across phenotypes-specific subgroups. LEVEL OF EVIDENCE: Level II, randomized controlled trial.