Have you ever come across the term “loose bodies”? If you have, it might possibly be because:
- You’ve just had an x-ray that has detected some in your own knee
- You can feel something loose in your knee and you’ve been googling the possibilities
- You have pain or problems flexing your knee, and you wonder if loose bodies might be the cause
All those possibilities are good reasons to find out more about this surprisingly common knee condition. So what exactly are loose bodies and what, if anything, can you do about them?
What are they?
A loose body is essentially a fragment of cartilage or bone that has broken away from the surface of the knee joint. Sometimes the fragment remains in situ. Sometimes it becomes truly “loose”, floating freely in the thick synovial fluid that protects and lubricates our joints (this is known as an “unstable” loose body). You may even be able to feel them underneath the skin.
What causes loose bodies?
The most common cause is trauma – some kind of injury you’ve sustained in an accident, a fall, a sporting twist or tackle. Another possibility is degeneration, where wear-and-tear has caused the articular cartilage in your joint to fragment and break away from the joint surfaces.
How big are they?
Loose bodies can be microscopic. By the time we see them in clinic, the average size is about 5 to 10mm. But they can get bigger as new cells develop on the fragment surface, or if it calcifies or ossifies. We often liken this to the effect of a pearl in an oyster. Loose bodies can grow quite substantially, even up to the size of a golf ball.
How serious are they?
Loose bodies usually aren’t a problem until they start causing irritating symptoms. The most obvious symptom is, of course, pain – and sometimes swelling or inflammation. But if they move into a joint they can cause mechanical problems too, such as locking or jamming, where you suddenly can’t flex or fully extend your knee. Sometimes this can make it hard to walk.
What should you do about them?
The first important step is to work out exactly what’s happening in your knee. A loose body that pops up on an x-ray won’t necessarily tell the whole story. It may be an indication of deeper damage that needs to be properly investigated – a cartilage injury, for example, or osteoarthritis. So before going any further, we need to take a full history and do some examinations to work out the next steps.
When do they need to be removed?
Loose bodies don’t always need to be removed – some simply settle, without causing noticeable symptoms. But if they become large and start to cause mechanical problems, we would probably recommend keyhole surgery to remove them (although open surgery is sometimes necessary in rarer cases). The operation involves making two very small incisions on either side of your knee. We then insert a tiny camera probe into one of the cuts so we can see what’s going on inside. Once we’ve investigated and located the fragment/s, we can carefully remove them with the surgical device. The operation is usually done under a general anaesthetic and takes around 30 minutes to complete.
It usually takes about two to four weeks to recover from a keyhole operation to remove loose bodies. But most patients find it’s worth the trouble. Rather like the proverbial pearls, loose bodies can be a cause of real irritation. Removing them is usually straightforward, however, and in most cases is enough to resolve the problem.
Find out more about how keyhole surgery works
Read more about other kinds of surgery for cartilage repair
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