Your knee contains a c-shaped pad of cartilage called the meniscus which cushions your femur (thigh bone) and your tibia (shin bone). Any wear or tear damage on that area makes that cushion degenerate and become less effective. For many patients with bone on bone knee pain, the cause is from overuse or overworked muscles that become shortened and imbalanced over time. This results in the compression of the thigh bone and shin bone which will eventually wear down the meniscus. The overly compressed knee joint will cause chronic pain and also prevent patients from moving their knees in a normal range of motion (bending and extending).