Loose Body in the Knee

What is a loose body?

A loose body is a fragment of bone, cartilage or both that has become detached and is now floating freely inside the knee joint. Some are small and barely noticeable; others are larger and cause significant problems.

Loose bodies can come from various sources — a previous injury that broke off a fragment, an osteochondral injury, advanced osteoarthritis, or conditions like osteochondritis dissecans. Sometimes the source is clear; sometimes the fragment has been in the joint for years before causing problems.

Because they move around with knee movement, loose bodies can produce symptoms that come and go in confusing ways.

What does it feel like?

The classic story is intermittent symptoms, often including:

• Sudden locking — the knee gets stuck and won't fully straighten or bend

• A sharp catching sensation when moving in particular positions

• Episodes of giving way

• Pain that comes and goes depending on the day

• A feeling that something is moving inside the joint

Many people can demonstrate where the loose body sometimes sits — they can feel it under the skin in certain positions, and it disappears in others.

How is it diagnosed?

The history is often diagnostic — episodes of locking with a clear catch-and-release pattern strongly suggest a loose body. Examination may identify a palpable fragment or reveal signs consistent with the diagnosis.

X-rays often show bony loose bodies. Soft cartilaginous fragments may need MRI to be visualised. Some loose bodies are only definitively identified at the time of keyhole surgery.

What are the treatment options?

Symptomatic loose bodies are almost always treated by removing them surgically. This is typically done as a straightforward keyhole (arthroscopic) procedure with a relatively quick recovery.

It's also worth understanding why the loose body formed in the first place — addressing the underlying cause where possible reduces the risk of recurrence. Nev will work through both aspects with you at your consultation.

When should you get it checked?

Seek a specialist assessment if:

• The knee locks intermittently and you can't fully straighten it

• You experience sharp catching with particular movements

• You can sometimes feel a fragment under the skin

• The knee gives way without warning

• Symptoms are interfering with sport, work or daily activities

Loose bodies are usually well-treated and the procedure to remove them is well-established. There's rarely a reason to live with the symptoms.