The knee joint is a very complex joint due to the many ligaments in and around the knee as well as the muscles and bones that surround the structure. The femur connects to the tibia (shin bone) where they meet is the knee joint. Anterior to the structure of the knee joint is the patella a small sesamoid bone. Lateral to the tibia is the fibula. In this structure you will find many ligaments and tendons of muscles that support the knee joint as well as mobilize it. Sitting on top of the Tibia there are two C-shaped discs know as the Menisci; the lateral menisci and the medial menisci. The role of both of these menisci is to absorb shock by dissipating forces out and deepen the tibia articulation increasing joint stability. The medial meniscus is attached to the medial collateral ligament (MCL) and the joint capsule. If there was ever damage to the MCL it is possible that the medial meniscus is torn. The lateral meniscus is smaller and does not have extra attachments it is just attached to the tibia. Around any joint you will most likely find these fluid filled sacs know as bursae which help reduce wear and tear on the joint. In the knee joint there are 4 bursae which help lubricate the knee so it can reduce tearing.
There are 4 movements of the knee joint those being knee Extension an action produced by the quadriceps tendon, Flexion an action made by the hamstrings, gracilis, sartorius and the popliteus, Lateral Rotation an action produced by one of the hamstring muscles; the biceps femoris, and finally Medial Rotation an action produced 2/3 hamstring muscles that include semimembranosus, semitendinosus it also includes other muscles like gracilis, sartorius and popliteus.
Patellar Ligament; this is a continuation of the quadriceps tendon which attaches to the tibial tuberosity.
The Collateral Ligaments
Medial Collateral Ligament (MCL): which is found on the medial side (close to the midline) of the knee joint it attaches at the medial epicondyle of the femur and to the medial condyle of the tibia.
The Lateral Collateral Ligament (LCL): found on the lateral side of the knee joint attaches to the lateral condyle of the femur and the lateral surface of the head of the fibula.
The Cruciate Ligaments which connect the femur and the tibia and they cross over each other hence the word cruciate.
The Anterior Cruciate Ligament (ACL): attaches at the anterior aspect of the tibia and blends in with the medial meniscus. It ascends posteriorly and attaches to the femur this ligament prevents an anterior sliding of the tibia on the femur.
The Posterior Cruciate Ligament (PCL): attaches at the posterior aspect of the tibia and ascends anterior to attach at the medial femoral condyle. This ligament prevents posterior dislocation on tibia on the femur.