The knee joint is made up of three bones: the femur (thigh), tibia (shin) and patella (knee cap). These bones are covered by a protective substance, called articular cartilage, enabling easy, smooth movements. Another type of cartilage, meniscal cartilage, acts as a cushion between the bones and a stabilizing platform for the knee. Each knee has two of these half-moon-shaped wedges of cartilage:
The lateral meniscus – on the outside of the knee
The medial meniscus – on the inside of the knee
Just as the articular cartilage protects the ends of our bones, the meniscus protects the articular cartilage from damage. Knees are designed to withstand the pressures of a lifetime of walking, running, sitting and standing. However, in many cases, the joint’s delicate balance is disturbed. Traumatic injury may cause the meniscus to tear, or may give rise to defects in the articular cartilage. Over time, small defects in the cartilage can worsen, leading to more widespread damage and eventually causing the pain and disability of arthritis. Alternatively, other non-traumatic forms of arthritis and various medical conditions can lead to articular cartilage damage.