The Earth is no longer a square, the knee was never a hinge

摘要

Until the Middle Ages it was thought that the Earth was flat and lay in the middle of a big ocean. With the development of better astron- omy and long-distance travel, this myth was debunked. 1 Initially, total knee arthroplasty (TKA) involved a hinged joint linking the femur and tibia. Improved understanding of anatomy and biomechanics allowed the development of an unconstrained total condylar knee.