We look at the latest in regenerative medicine for treating knee problems. Osteoarthritis happens when the meniscus and cartilage wear out. Researchers aim to repair meniscal damage with autologous synovial stem cell transplants. Ligament tears, an injury common among athletes, are also usually treated with transplants using the patient's own tendons or artificial ligaments. A bovine tendon has successfully been transplanted into a sheep, and a clinical trial will soon begin for use in humans.