This is a small piece of bone, cartilage, or foreign body that becomes caught in between two bones causing sudden, sharp pain and occasional giving away. The knee is the most common site for loose bodies. There is usually a catching feeling and swelling of the affected joint. Occasionally, the joint actually becomes locked. This is usually self-limited.
- Injury (chip fracture)
- Torn piece of cartilage
- Foreign body
The loose body is often seen on a regular x-ray. Sometimes, an MRI is ordered to see a loose piece of cartilage that does not have any bone in it (you can’t see those on regular x-rays). Also determining where the loose body came from is important and may also require treatment.
If the loose body continues to cause symptoms or other damage they usually can be removed with a procedure called an arthroscopy. Again focusing attention to the site where it originated may also need treatment so this does not continue to cause further problems.