Knee Anatomy

Knee Anatomy

The knee is one of the most important joints in the body. It is a large, complex joint consisting of two articulations. An articulation refers to two locations where bones meet to allow movement. In the knee the two articulations are:

  •  between the Femur (thigh bone) and the Tibia (Shin bone)
  • between the Femur and the Patella (knee cap).

The knee is a complex joint of ligaments, muscles and tendons that all play a crucial role – read on to find out more about each of these structures. Movement at the knee joint is essential for most day-to-day activities such as walking and running. The knee is vulnerable to acute injuries – such as those sustained during contact sports.


There are two types of cartilage in the knee. The meniscus and articular cartilage. Cartilage is the coating at the end of long bones that allows frictionless movement. It has a complex structure consisting of a matrix, water, and cells (chondrocytes). It has no blood supply, and does not regenerate when damaged.

  • MENISCUS  – The menisci are two crescent-shaped structures whose function is to distribute load evenly to the femur .The two menisci are the medial (on the inside of the knee) and lateral (on the outside of the knee).
  • ARTICULAR – This is found on the femur, top of the tibia and the back of the patella. It is a thin layer of cartilage that acts as a shock absorber but also enables the bones to move smoothly over each other. Pain caused by damage to the menisci or articular cartilage is a commonly seen problem.

Ligaments are thick fibrous bands (similar to ropes) whose job it is to hold the bones together. Knee ligaments are split into two groups;

  • Collateral ligaments that are on the outside of the joint
    • Medial Collateral ligament (MCL) is on the inside of the knee and it’s job is to resist against impacts from the outside of the leg
    • Lateral Collateral ligament (LCL) is on the outside of the knee and it’s job is to resist against impacts from the inside of the leg. It is much less common for the LCL to get injured.

Athletes playing contact sports such as rugby and football are at a higher risk of collateral ligament injuries, especially with potential for direct blows to the outside of the knee.

  • Cruciate ligaments are found INSIDE the joint
    • Anterior cruciate ligament (ACL) sits deep inside the middle of the joint and is the primary structure for stability within the knee.  This ligament is commonly injured in sporting activities as a result of twisting and sudden stopping movements.
    • Posterior cruciate ligament (PCL) attaches the back of the tibia and the front of the femur. Although it is shorter than the ACL it is stronger and therefore not injured as often as the ACL. The most common cause of PCL injury is high impact trauma such as a car accident or extreme force during a contact sport.

Good strength and flexibility in the knee muscles is very important as any weaknesses will leave you more prone to injury.  The two main groups of muscles in the knee are;

  • Quadriceps – a group of 4 muscles that are at the front of the thigh and go over the knee. The main function of these muscles is to straighten the leg. They also Work with the glutes (bottom muscles) and hamstrings to enable us to walk, run and jump as well as controlling movement of the knee cap.
  • Hamstrings – a group of 3 muscles found at the back of the knee and whose job it is to bend and rotate the knee. They help to stabilise the knee and protect the knee ligaments as well as allowing us to lift our legs off the ground when walking etc. It also provides the strength that we need in order to perform task like running and jumping.

The conditions mentioned above are only some of the things that can go wrong in the knee. Another common condition in Athletes is patella tendinitis – you can read more about this condition here

The important points to remember are:

  • Look after your joints and all the structures that support and work with them. This includes using the right equipment and warming up/down properly.
  • Accurate, correct and timely diagnosis and subsequent treatment are important and will greatly increase your chances of a full and quick recovery. It may even been the difference between needing surgery and not!


You can read more into the knee structures on our Knee information pages


Posted in .