Knee Anatomy
The large joint of the body, the knee joint is the weight-bearing joint, that is most commonly affected by arthritis.
The knee joint helps the leg perform extension, flexion, forward and backward movements, and restricted side-to-side movements. The bones, cartilage, ligaments, tendons, and muscles form the knee joint.
The bottom of the femur bone, the top of the tibia bone, and the back of the patella come in contact with each other at the knee joint. The touching parts of these bones are covered by articular cartilage, which is flexible, hard, and very smooth. Articular cartilage allows the bones to move over each other smoothly.
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When there is the development of osteophytes over the cartilage, then the smooth movement is hindered and friction is created.
There are two menisci inside the knee joint, the medial meniscus and lateral meniscus, they help the movement of the femur and tibia over it and take the shock of the knee during movement and weight-bearing.
There are four main ligaments, the anterior cruciate ligament (ACL); posterior cruciate ligament (PCL), medial collateral ligament (MCL), and lateral collateral ligament (LCL). The ACL and PCL control the forward and backward movement of the tibia and the MCL and LCL control the sideways movement of the knee joint. The ligaments join one bone to the other.
The tendon joins the bone to the muscle. The patellar tendon is the largest tendon, which covers the patella and attaches itself to the quadriceps muscles.
The leg straightening is because of the contraction of the patellar tendon. There are many fluid-filled sacs inside the knee joint known as the bursa, which is located between the bone and soft tissues. They also help in friction reduction between the bone and soft tissues.
The knee joint is encapsulated by a thin membrane known as the synovial membrane, it’s basic function is to provide nutrients to the joint and the viscous fluid released by this membrane provides lubrication to the knee joint. When the knee joint moves, this fluid is released.
Two strong and flexible muscles also support the knee joint. The quadriceps muscles lie over the thigh and the hamstrings lie under the knee. These two muscles help in extension and flexion of the knee joint.
