Anatomy of the Knee
The knee is a significant mobile component of the body made up of three bones: the patella (kneecap), the tibia, the shin bone and the femur, also referred to as the thigh bone. Due to the complexity and overuse of the joint, the knee is susceptible to injury or general wear over the years.
Also known as a synovial joint because of the liquid-filled capsule inside the joint, the knee is created to perform the following functions:
- Provide support and stabilise the body when in an upright position
- Absorbs shock
- Enables the twisting motion of the leg
- Assists with walking by propelling the body forward
The Cartilage of the Knee
The menisci, the C-shaped discs of cartilage that cushion and protect the bones of the knee, are classified as the shock absorbers of the knee joint. Each knee is designed to have two menisci-
- One on the inner part of the knee, which is considered the largest.
- One on the outer part of the knee.
The knee's ligaments are sturdy fibrous cords that attach the bones, preventing unnecessary and excessive motion.
The knee is made of four major ligaments that help stabilise the joint:
- The anterior cruciate ligament (ACL) restricts the sliding motion of the femur, preventing it from moving backwards and colliding with the tibia. As a result, the tibia cannot collide with the femur from the front.
- The posterior cruciate ligament (PCL) prevents the forward sliding motion of the femur onto the tibia. In addition, because of the PCL, the tibia cannot slide back onto the femur.
- The medial collateral ligament (MCL) restricts excessive mobility of the femur, preventing it from moving from one side to the other.
- The lateral collateral ligament (LCL) limits side to side motion of the femur.
Tendons of the Knee
The knee is also comprised of soft but tough tissue bands called tendons. However, instead of connecting one bone to another, the way ligaments do, tendons are made to link muscle to bone. The patellar tendon is an expansive tendon in the knee that engulfs the kneecap, travels up the thigh and connects to the quadriceps.
Muscles of the Knee
Muscles like the quadriceps and hamstrings help extend the knee. The quadriceps muscles assist by straightening the knee, and the hamstrings, which are three muscles behind the thigh, help by bending the knee.
Joint Capsule & Bursa
The joint capsule is classified as a “membrane bag” that encases the knee joint. Synovial fluid fills the capsule, which is essential for lubricating the joint. Approximately 14 liquid-filled sacs (bursa) remain inside the knee joint. The bursa helps reduce friction and inflammation in the knee.
