The knee is not only one of the largest and most complex joints in the body—it is also easily injured. In fact, one of the most common orthopedic injuries is the tearing of the meniscus, a half-moon-shaped piece of cartilage in the knee. Each knee has two menisci that allow the joint to move freely. Current treatments for a torn meniscus are less than ideal, involving removing or repairing the torn segment, which can ultimately lead to increased risk of arthritis or knee replacement, as the affected joint loses its cushioning.