Knee anatomy – How the knee joint is constructed

Last modified: December 11, 2019

The knee is one of the largest joints in the body, as well as being one of the most sensitive ones. This is because this joint comprises several components that make it prone to injury. When looking at the knee anatomy, there are four main components that form the joint. These are are the skeleton bone, cartilage, ligament, and menisci. The knee joint has a joint capsule around it and then muscles. The kneecap is inside the large thigh muscle at the front and stabilizes the joint. The thighbone and lower leg are attached to each other by ligaments and muscles. Ligaments are also frequently mentioned when referring to the knee.

Ligaments in the knee

The knee, or knee joint to be more specific, is the most complicated joint in the body. This is because the knee is made up of various ligaments that help hold the joint together. There are two tight ligaments inside the knee, known as cruciate ligaments. They stabilize the joint’s forward and backward movement.

The knee has another type of ligament at either side of it, known as the collateral ligament. Its purpose is to stabilize the joint’s sideways movement. Unfortunately, ligament injuries are common. A cruciate ligament injury can occur, for instance, in the event of quick twists of the knee and of tackles, which usually occurs in different types of sport. The collateral ligament can get injured if a load is suddenly exerted on it from the side, such as in the case of a tackle or fall. 

What is cartilage?

The knee joint is what is known as a hinge joint. This means that it can only be bent in one direction. To enable a joint to glide easily, the ends of the skeleton are covered with cartilage, which includes the knee joint. Cartilage is an important component in the knee’s structure and helps both ensure stability and absorb any impact. Joint cartilage comprises cartilage cells and tissue. As cartilage does not receive any oxygen supply via the blood vessels, this makes it very difficult to form again if it gets damaged.

When the cartilage breaks down, which can happen to anyone whose joints are subject to overexertion over a lengthy period of time, this is called osteoarthritis. Osteoarthritis is the world’s most common joint disease. Common symptoms are stiff, painful joints.

Continue reading about osteoarthritis.

Menisci

The knee has two joint surfaces. The top one is made up of the lower part of the thighbone and the bottom of the top part of the shinbone. To enable the best possible fit to be achieved and stabilize the knee, there are two cartilage discs placed between the joint surfaces, one on the outside of the knee and the other on the inside. These are called menisci. They got their name from the Greek work for “crescent” as they have a crescent shape. The meniscus makes the knee more stable during movement and also acts, just like the joint cartilage, as a shock absorber.

The menisci are fairly sensitive and can get injured if you twist your knee dramatically or if they sustain a blow. However, the most common injury to the meniscus occurs through wear and tear, which is a gradual process. This is known as a degenerative meniscal injury. The reason for this is that the meniscus gets increasingly worn as the years go by and can gradually break or burst. In these cases, rehabilitation exercises are helpful. If they fail to give a successful outcome, keyhole surgery may be required.

Read more about the anatomy of the hip.