Knee Anatomy

What does the knee consist of?

The knee is one of the largest and most important joints in the human body. It functions primarily as a hinge joint, allowing the leg to bend and straighten while also permitting limited rotational and side-to-side movement. The knee plays a vital role in standing, walking, running, jumping, and maintaining balance. Its stability and movement depend on a complex interaction of bones, cartilage, ligaments, tendons, muscles, and supporting soft tissues.

What bones form the knee joint?

The knee joint is formed by three main bones that work together to allow movement and weight-bearing:

The femur (thighbone) forms the upper part of the joint and connects with the tibia.

The tibia (shinbone) forms the lower part of the joint and supports most of the body’s weight.

The patella (kneecap) sits in front of the knee and glides within a groove at the lower end of the femur, helping improve movement efficiency and protect the joint.

What is the function of cartilage and meniscus?

The ends of the femur, tibia, and patella are covered with articular cartilage, a smooth, protective tissue that reduces friction and allows the bones to glide easily during movement. It also acts as a shock absorber during weight-bearing activities.

Inside the knee are two crescent-shaped cartilage structures called the menisci:

• The medial meniscus
• The lateral meniscus

These structures help distribute body weight evenly across the knee joint, absorb shock, and improve joint stability during movement such as walking, running, and jumping.

What ligaments support the knee?

Ligaments are strong fibrous tissues that connect bone to bone and provide stability to the knee joint. The four major ligaments include:

• Anterior cruciate ligament (ACL) – prevents forward movement of the tibia and stabilises rotational movement
• Posterior cruciate ligament (PCL) – prevents backward movement of the tibia
• Medial collateral ligament (MCL) – stabilises the inner side of the knee
• Lateral collateral ligament (LCL) – stabilises the outer side of the knee

Together, these ligaments ensure controlled movement and prevent excessive motion that could damage the joint.

What tendons are important in the knee?

Tendons connect muscles to bones and allow movement of the knee joint.

The most important tendon in the knee is the patellar tendon, which connects the quadriceps muscle group to the tibia via the patella. It plays a key role in straightening the leg and supporting activities such as walking, running, and jumping.

The quadriceps tendon, located above the patella, also contributes to knee extension and stability.

What are bursae and what do they do?

Bursae are small fluid-filled sacs located around the knee joint. They reduce friction between bones, tendons, and muscles, allowing smooth and pain-free movement.

These structures act as cushions that protect soft tissues from irritation during repeated movement and pressure.

What is the synovial membrane and synovial fluid?

The knee joint is surrounded by a thin lining called the synovial membrane. This membrane produces synovial fluid, which lubricates the joint, reduces friction, and nourishes the cartilage.

Synovial fluid plays an essential role in ensuring smooth, pain-free movement of the knee.

What muscles support the knee?

Several muscle groups work together to move and stabilise the knee joint:

Quadriceps muscles at the front of the thigh help straighten the knee.

Hamstring muscles at the back of the thigh help bend the knee and control movement. Muscles in the lower leg also contribute to balance, stability, and coordinated movement.

These muscles work in coordination to support walking, running, jumping, and other daily activities.

Why is the knee important?

The knee is essential for mobility and weight-bearing function. It absorbs force, provides stability, and allows controlled movement between the thigh and lower leg. Because it carries significant body weight and is involved in almost all lower-limb movement, it is also highly susceptible to injury and degenerative conditions such as osteoarthritis.