Anatomy of the knee
Find out more about the anatomy of the knee
The knee is one of the largest and most complex joints in the body. The knee joins the thigh bone (femur) to the shin bone (tibia). The smaller bone that runs alongside the tibia (fibula) and the kneecap (patella) are the other bones that make the knee joint. Knee anatomy is about the structure of the knee – that is the parts that makeup the knee. This article also tells you how a normal knee works and provides resources for problem of the knee joint or it’s parts including knee injuries.
The knee joint is a synovial joint which connects the femur, our thigh bone and longest bone in the body, to the tibia, our shinbone and second longest bone. There are two joints in the knee—the tibiofemoral joint, which joins the tibia to the femur and the patellofemoral joint which joins the kneecap to the femur. These two joints work together to form a modified hinge joint that allows the knee to bend and straighten, but also to rotate slightly and from side to side. The knee is part of a chain that includes the pelvis, hip, and upper leg above, and the lower leg, ankle and foot below. All of these work together and depend on each other for function and movement. The knee joint bears most of the weight of the body. When we’re sitting, the tibia and femur barely touch; standing they lock together to form a stable unit. Let’s look at a normal knee joint to understand how the parts (anatomy) work together (function) and how knee problems can occur.
Important information about the knee joint capsule
The joint capsule is a thick ligamentous structure that surrounds the entire knee. Inside this capsule is a specialized membrane known as the synovial membrane which provides nourishment to all the surrounding structures. The synovial membrane produces synovial fluid which lubricates the knee joint. Other structures include the infrapatellar fat pad and bursa which function as cushions to exterior forces on the knee. The capsule itself is strengthened by the surrounding ligaments.
And what about the ligaments of the knee joint?
The stability of the knee owes greatly to the presence of its ligaments. Each has a particular function in helping to maintain optimal knee stability in a variety of different positions. The medial Collateral Ligament or MCL for sort is a band that runs between the inner surfaces of the femur and the tibia. It resists forces acting from the outer surface of the knee called valgus forces and prevents the knee from collapsing inwards. The medial knee ligament has two parts to it; an inner part which attaches to the cartilage meniscus on the inside of the knee and an outer part with attaches to the tibia bone.
The lateral Collateral Ligament or LCL is on the outside of the knee and joins the outer surface of the femur to the head of the fibula. It resists impacts from the inner surface of the knee known as varus forces. The anterior Cruciate Ligament or ACLis one of the most important structures in the knee, not least because injury to it may require extensive surgery and rehabilitation. The cruciate ligaments are so called because they form a cross in the middle of the knee joint. The ACL, travels from the anterior or front of the tibia to the posterior or back of the femur and prevents the tibia moving forward. It is most commonly injured in twisting movements. The posterior Cruciate Ligament or PCL attaches from the posterior or back surface of the tibia to the anterior or front surface of the femur and in doing so wraps around the ACL. The posterior cruciate ligament prevents the knee joint from being bent back the wrong way.
MUSCLES and TENDONS – what are their role in the anatomy of the knee
Tendons connect muscles to bone. The strong quadriceps muscles on the front of the thigh attach to the top of the patella via the quadriceps tendon. This tendon covers the patella and continues down to form the "rope-like" patellar tendon. The patellar tendon in turn, attaches to the front of the tibia. The hamstring muscles on the back of the thigh attach to the tibia at the back of the knee. The quadriceps muscles are the main muscles that straighten the knee. The hamstring muscles are the main muscles that bend the knee.