Normal Anatomy of the Knee Joint

The knee joint, one of the most important joints of the human body, is composed of three bones – the (1)femur, or thighbone, the (2)tibia, also known as the shinbone, and the (3)patella, or kneecap. The union of these three bones is what enables the knee joint to move fluidly with protection.

Extension of the knee is supported by synovial fluid and the synovial membrane. This specialized connective tissue lines the interior of the knee joint and provides it with lubrication to ensure smooth movement. Inside the joint you will also find a host of connective tendons, ligaments, and other soft tissues.

Femur

The Femur, also known as the thighbone, is the largest and the strongest bone in the human body. It is also the single most important weight-bearing bone and the only bone in the upper leg. Additionally, it connects into the acetabulum, or hip socket, to form the hip joint.

Fibula

The fibula, known more commonly as the calf bone, is located next to the tibia and provides the leg with additional structural integrity. The fibula itself will add support to the leg as well as a surface for surrounding muscle and tendon tissue to attach to.

Condyle

The femoral bone has two condyles, or rounded heads, that allows it to fit tightly and smoothly within the hip socket on one end and the knee joint on its bottom end.

Menisci

The menisci are two crescent-shaped pads of soft cartilaginous tissue, located between the femur and the tibia. The menisci work to absorb the majority of the shock that the knee joint experiences. Menisci also provide a fluid surface for the bones that make up the knee joint to move with little to no friction.

Patella

The patella, or kneecap, has an irregular shape with a rough base at the top, where it attaches to the femur, and a rounded bottom, where it supports the patellar tendon.

The patella is the central point of connection between the quadriceps and the patellar tendon. Additionally, the kneecap, as its name suggests, rests atop the knee and protects the underlying bones, tissues and tendons from trauma.

Tibia

The tibia, or shinbone, is a large, weight-bearing bone of the leg below the knee joint. Next to the femur, it is the second largest bone in the body. The tibia serves as a connection between the knee joints and the ankle joints.

Medial Collateral Ligament (MCL)

The Medial Collateral Ligament, as with the other key ligaments within the knee, plays the important role of providing stability and support for the knee joint. The MCL lies within the interior part of the knee and protects against over extension of the knee joint into the body.

Posterior Cruciate Ligament (PCL)

The Posterior Cruciate Ligament extends from an area behind the tibia to the femur. The Posterior Cruciate Ligament prevents the tibia from sliding off the femur during knee extension and movement. Just as the ACL, the PCL provides a significant degree of stability to the knee, especially during rotational movements.

Anterior Cruciate Ligament (ACL)

The Anterior Cruciate Ligament, being one of the major stabilizing ligaments of the body. It is located behind and the patella connects the femur to the tibia. This connection prevents the knee joint from dislocating. Injuries to the anterior cruciate ligament significantly reduce the knee joint’s functional integrity and impose severely limiting mobility restrictions.