Robotic-assisted knee arthroplasty methods provide insight into Homo neanderthalensis gait and the evolutionary origins of modern human knee variation

Abstract

Abstract Lower-limb alignment is central to human bipedal locomotion and a key determinant of joint kinematics and osteoarthritis risk in modern clinical practice. However, its significance in hominins, and therefore its evolutionary implications, remain poorly understood. Advances in robotic-assisted total knee arthroplasty (TKA) provide highly precise measurements of lower-limb alignment, joint morphology and soft-tissue balance that can elucidate these understudied aspects of hominin functional morphology. Here, we perform a proof-of-concept robotic-assisted TKA on an anatomically accurate model of the Spy II Neandertal. Using a robotic-assistance system, we registered bony morphology and replicated soft-tissue laxity extrapolated from a modern patient with a comparable alignment phenotype. We confirmed a pronounced constitutional varus alignment, classifying Spy II as a CPAK type I knee. This phenotype resembles that of modern athletes engaged in significant weight-bearing sports or intense physical activity during growth. The demonstration of constitutional varus in a hominin fossil thus suggests a deep evolutionary origin for this alignment pattern in modern humans, contextualizing normal knee variation and supporting an individualized alignment approach to modern TKA.

The authors' abstract, as published at the source. Scientific Reports, 2026 · DOI ↗