Hip or knee joint wear seen by chance on an X-ray or scan

What the report means

Cartilage wear. In a healthy joint, the bone ends are covered with smooth cartilage. In osteoarthritis the cartilage breaks down and becomes rough. (MedlinePlus) On an X-ray, thinner cartilage shows as a narrower gap between the bones, often reported as "joint space narrowing".
Bone spurs (osteophytes). Bumps of extra bone called bone spurs may grow around the joint. (MedlinePlus)
Other MRI words. A knee MRI may also list cartilage defects, meniscal tears or bone marrow lesions. A review of MRI studies counts all of these as features of osteoarthritis that are often seen in knees without pain. (Culvenor 2019)
Not everyone has pain. Osteoarthritis affects people in different ways, and not everyone has pain. (MedlinePlus)

How common these changes are with age

Knees without pain or injury. A review of 63 MRI studies covering 4,751 adults with no knee pain or injury found cartilage defects in 11% of those under 40 and 43% of those 40 and over, and meniscal tears in 4% and 19%. Bone spurs were seen in 25% overall and became more common with age. (Culvenor 2019)
Hips in a US town. In the Framingham community, 19.6% of people had hip osteoarthritis on an X-ray, but only 4.2% had it with symptoms, as quoted by the authors of a 2015 hip study. (Kim 2015)
Who is more likely to have it. The chance rises with age, and after 50 it is more common in women than men. (MedlinePlus) The NHS also lists past joint injury, other joint conditions such as gout or rheumatoid arthritis, and family history. (NHS)

Why the picture and symptoms often do not match

Knees. Across population studies, 15% to 81% of people with knee osteoarthritis on an X-ray had knee pain, depending on how pain and the X-ray were judged. The review concludes that knee X-rays should not be used alone to assess a person. (Bedson 2008)
Hips. In two US studies of people aged 50 and over (946 and 4,366 people), only 20.7% and 23.8% of hips with osteoarthritis on an X-ray were painful on most days. And only 15.6% and 9.1% of hips that were often painful showed osteoarthritis on the X-ray. (Kim 2015)
What guidance takes from this. NICE advises diagnosing osteoarthritis without imaging in people aged 45 or over who have joint pain on activity and no morning stiffness, or stiffness lasting 30 minutes or less. (NICE NG226)

Signs that need a check

Symptoms that last. The NHS advises seeing a GP if you have lasting joint pain, stiffness or trouble moving a joint, so they can confirm the diagnosis. (NHS)
Unusual features. NICE lists features that call for more than a clinical diagnosis: a recent injury, morning stiffness that lasts a long time, symptoms or joint shape getting worse quickly, a hot swollen joint, or concerns about infection or cancer. (NICE NG226)
Other causes. Long morning stiffness can be a sign of rheumatoid arthritis, and X-rays or blood tests may be used to rule out other causes such as a broken bone. (NHS)
Worry is real. See after an abnormal screening result.

How it ties to your age-based checks

Joint wear found by chance is a good moment to make sure your routine checks are up to date:

Other bone and joint findings have their own pages: disc bulge or wear on a spine scan, low bone density seen on a CT, a bone spot found by chance and screenings if you have gout.

Who it applies to

Adults told that an X-ray, CT or MRI done for another reason shows wear in a hip or knee. Children, recent joint injuries and inflammatory joint conditions such as rheumatoid arthritis are outside this page.

NICE lists a hot swollen joint, symptoms or joint shape getting worse quickly, and concerns about infection as features that need more than a routine diagnosis. Contact your doctor promptly if you notice any of these. (NICE NG226)

Routine age-based screening

A finding on an X-ray or scan does not replace the routine screenings for your age. See screenings by age and gender.

Where they differ:

Using X-rays. NICE advises against routine imaging to diagnose osteoarthritis (NICE NG226), and the NHS says X-rays are not usually needed but may rule out other causes. (NHS) The authors of a US hip study warn that relying only on hip X-rays may miss many cases. (Kim 2015)
How it changes over time. MedlinePlus says osteoarthritis usually gets worse slowly (MedlinePlus), while the NHS says it does not necessarily get worse and can sometimes gradually improve. (NHS)
How common. Figures vary widely with the type of scan, the X-ray view, how pain is defined and the group studied. (Bedson 2008)(Culvenor 2019)

Your doctor decides what your result means for you.

Questions people ask

Does joint wear on my scan mean I have osteoarthritis?

Not on its own. NICE advises diagnosing osteoarthritis from symptoms and an examination, without imaging, in people aged 45 or over with joint pain on activity and little or no morning stiffness. A review of knee studies says X-ray results should not be used alone to judge a person with knee pain. (NICE NG226) (Bedson 2008)

How common is joint wear in people without pain?

Common. In a review of 63 MRI studies of adults with no knee pain or injury, cartilage defects were seen in 43% of those aged 40 and over and bone spurs in 25% overall, rising with age. (Culvenor 2019)

Why do I have no pain if the scan shows wear?

The picture and symptoms often do not match. In two large US hip studies, only about 1 in 5 hips that showed osteoarthritis on an X-ray were painful on most days. (Kim 2015)

Will it get worse?

Sources differ. MedlinePlus says osteoarthritis usually gets worse slowly, while the NHS says it does not necessarily get worse over time and can sometimes gradually improve. Your doctor decides. (MedlinePlus) (NHS)

Do I need another X-ray or scan?

NICE advises against routine imaging to diagnose osteoarthritis or to follow it up, unless there are unusual features or signs of another condition. Your doctor decides. (NICE NG226)