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Parts of the Knee Joint

The knee may appear relatively simple as a necessary rotation function, but it is the most complex joint in the human body. Several different parts make up the knee, all of which need to be healthy if the knee is to function to its full capabilities. That is one of the reasons why knee injuries are so common.

  1. The Bones

    • The knee is surrounded by four bones. The main movements of our knee joint occur between our thigh bone, shin bone and kneecap (known medically as the femur, tibia and patella respectively). Sitting beside the tibia is the fibula, which is our outer shin bone that travels all the way down to our ankle joint. These bones are all covered in what is known as articular cartilage, a hard but smooth substance designed to decrease the friction between the bones when we are moving.

    The Knee Capsule

    • Between the knee bones is a water-tight casing, known as the knee capsule. The structure surrounds the entire knee and excretes a membrane that gives nourishment to the surrounding areas of the knee. This area can be filled with fluid, causing our knees to swell up when injured.

    The Ligaments

    • The stability of our knees hinges on the health of our knee ligaments. These are four sets of soft tissues which band together the bones. The medial collateral ligament, MCL, goes between the inner surface of the femur and tibia. The lateral collateral ligament, LCL, runs between the outer side of the femur to the top of the tibula. The other two ligaments are the anterior and posterior cruciate ligaments, ACL and PCL, which cross over each other at the center of the knee joint. They keep the femur and the tibia together and are synonymous with sporting injuries.

    Knee Cartilage

    • Two crescent-shaped areas of tissue sit on top of the tibia. They are stationed at both the inner and the outer surfaces of the thigh bone. They help to distribute the weight of both the femur and tibia while acting as shock absorbers for the entire knee.

    Tendons

    • The muscles around the knee connect to the bones through tendons. First there is the quadriceps tendon which connects the four quadriceps muscles to the knee at the top of the knee cap. Then there is the patellar tendon which connects the patella and the tibia. Because it runs between two bones it is sometimes referred to as a ligament. The illiotibial band is a long tendon that connects a muscle running from the hip to the knee, which helps to provide flexibility for the joint. There is also the hamstring tendon that attaches the hamstring muscles to the tibia and fibula. It helps the knee to flex.

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