Joint distraction for knee osteoarthritis without alignment correction aims to offload and modify the mechanical environment in osteoarthritic joints to allow cartilage regrowth. Intra-articular surgery (such as debridement) may be done before distraction to stimulate cartilage healing.
With the patient under spinal block or general anaesthesia, pins are drilled through the tibia and femur. A distraction frame is then fitted external to the leg, unloading the knee by gradually increasing the distance between the cartilaginous surfaces of the knee (usually up to 5 mm) over a few days or weeks. The distraction is normally maintained for about 2–3 months before the frame is removed. During this time, the patient is able to walk. The continuous flow of synovial fluid through the joint (enhanced by the distraction) is claimed to support chondrocyte nutrition and regeneration of cartilage. However, the exact mechanisms that may lead to cartilage regeneration during distraction are not known.