There are a large number of ligaments in and around the knee. However, the femur and shinbones are mainly held in place by four ligaments that are important for the knee joint:
• The anterior cruciate ligament (ACL)
• The posterior cruciate ligament (PCL)
• The medial collateral ligament (MCL)
• The lateral collateral ligament (LCL)
The fairly frequent injury of one of these four ligaments can lead to instability of the knee joint in various directions.
The quadriceps muscles form a group of muscles which are attached to the kneecap by a common tendon. They are used to straighten the knee. The flexor muscles are a group of muscles attached to the tibia or fibula. They are used to flex the knee. The calf muscles are also involved in knee movement.