• Patellofemoral Compartment -- kneecap riding over the end of the femur "trochlea/sulcus" groove
• Medial Compartment -- the area of joint contact between the femur and tibia on the "inside" or medial aspect of the knee (bring your knees together and the medial aspects become closer)
• Lateral Compartment -- the area of joint contact between the femur and tibia on the "outside" of lateral aspect of the knee (the right side of a right knee and the left side of a left knee)

Cartilage is often used to refer to the C-shaped fibrocartilage pads between the femur and tibia at each compartment, thus a medial meniscal cartilage and a lateral meniscal cartilage. The broad term cartilage also has another subcategory--that of the articular or joint covering hyaline cartilage (the white, glistening, smooth soft, almost plastic-appearing living substance coating the ends of bones at a joint).

Either of these cartilage tissues can be injured or torn. This occurs more frequently with twists/ turns or the high forces of sports.

The ligaments are the very strong fibrous bands which connect bone to bone at a joint and in the knee are usually grouped as:

• ACL -- anterior cruciate ligament
• PCL -- posterior cruciate ligament
• LCL -- lateral collateral ligament
• MCL -- medial collateral ligaement