Surgeons once used carbon fiber to replace ligaments, but the body often rejected the material.

During the late 1970s and early 1980s, the search for the 'ideal' synthetic ligament led researchers to carbon fiber and polytetrafluoroethylene, commonly known as Gore-Tex. Carbon fiber was initially praised for its high tensile strength and its potential to act as a scaffold for new tissue growth. However, clinical studies soon revealed that the material was too brittle for the high-stress environment of the human knee joint.A significant study published in the Journal of Bone and Joint Surgery highlighted that carbon fibers would undergo mechanical fatigue and fragmentation. These microscopic fragments would migrate into the synovial membrane, triggering a condition known as synovitis. The body's immune system identified these particles as foreign invaders, leading to persistent swelling and the eventual degradation of the surrounding cartilage.By the mid-1990s, the failure rates for synthetic ligaments were reported to be as high as 40% to 50% within just a few years of implantation. This led the medical community to shift toward autografts, which use the patient's own patellar or hamstring tendons, and allografts from cadaver donors. These biological options are superior because they undergo a process called 'ligamentization,' where the body replaces the graft cells with its own living tissue, ensuring long-term durability and biocompatibility.