Knee Anatomy: Structure and Common Injuries

The knee joint

The knee is a large joint connecting the femur (thigh bone) to the tibia (shin bone). It's built to allow a large range of motion while staying stable and strong enough to handle serious load. For anyone who lifts, keeping the knee — and every other joint — functioning properly really matters.

The knee is a hinge-type joint, built for a large range of motion in a single direction. The lower end of the femur is rounded and fits precisely into the upper, bowl-shaped surface of the tibia. Both bone ends are covered in a tough but flexible whitish material — articular cartilage. The cartilage surface is coated in synovial fluid, produced by cells in the joint capsule that surrounds the whole joint. At the most heavily loaded points, fluid-filled sacs called bursae form to protect the knee from overload.

Inside the joint cavity are two cartilage pads called menisci. They're there to add stability and allow a greater range of motion. The menisci are also one of the most vulnerable parts of the knee, especially in sport — meniscus injuries frequently require surgery and sometimes partial or full removal. The knee can still function without a meniscus, but the cartilage wears down faster as a result.

Strength and stability come from the ligaments, positioned along the sides and back of the joint, holding the two bones firmly together without restricting the joint's movement. Knee movement itself is driven by the quadriceps (the four-headed muscle on the front of the thigh), which extends the leg, and the hamstrings, which flex it. These muscles attach near the hip or upper femur at the top, and taper into strong tendons lower down that attach to the tibia. The quadriceps tendon also houses the patella (kneecap), which prevents the tendon from rubbing directly against the joint.

A large network of blood vessels supplies the knee, nourishing the cartilage, ligaments, and joint capsule. It's worth taking joint health seriously and not treating it as an afterthought — a wide range of joint-support supplements exists for exactly this reason.