M23.4: Loose body in knee

The knee joint connects the thighbone (femur) to the lower leg. The kneecap is also part of the knee joint. There are 2 bones in the lower leg. These bones are called the tibia (shinbone) and fibula. There is also a joint immediately below the knee joint between the tibia and fibula.

In a joint, two or more bones come together. The bones are coated with a protective layer of cartilage. And joints are also encased in a capsule made of connective tissue. Inside the capsule there is always some fluid in the joint. It can happen, for various reasons, that a piece of bone, cartilage or connective tissue becomes detached. This piece can then move freely in the fluid in the joint. Reasons may include, for example, injuries or inflammation of the joint. After an operation, suture material may become detached so that it moves freely within the fluid in the joint. When something is moving freely within the joint, it is known as a loose body.

If loose bodies get jammed in the joint, it can cause pain. It may also no longer be possible to move the joint properly. The joint may then swell up.

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