Osteoarthritis on X‑ray

Written by the X-Ray Atlas editorial team from the sources listed below · Medical review pending · Updated 24 October 2026 · Level: Beginner

Osteoarthritis (OA) is the most common joint disease and the most common arthritis you will see on an X-ray. It is a disorder of the whole joint: cartilage thins, the bone underneath reacts, and new bone grows at the margins. The radiographic signs are summarised by the mnemonic LOSS. Learning OA well matters for two reasons. It is everywhere, so you need to recognise it quickly, and it is the baseline against which other arthritides are compared: features that do not fit OA should make you think of inflammatory, crystal or infective arthritis instead.

1. The four signs: LOSS

Sign	What it is	What to look for
Loss of joint space	Thinning of the articular cartilage, which is invisible on X-ray but occupies the joint space.	Narrowing that is asymmetric (focal), affecting the most loaded part of the joint: for example the medial compartment of the knee or the superolateral hip.
Osteophytes	New bone growing at the joint margins.	Spurs or lips of bone at the edges of the articular surfaces. Often the earliest definite sign.
Subchondral sclerosis	Thickened bone beneath the worn cartilage.	Increased whiteness of the bone just under the narrowed joint surface.
Subchondral cysts	Fluid-filled cavities (geodes) in the bone under the joint.	Rounded lucencies with thin sclerotic margins near the joint surface.

Just as important is what OA usually does not have: no periarticular osteopenia (bone density is normal or increased near the joint) and no marginal erosions. The exception is erosive OA, described below.

2. How to look

A useful system for any arthritis film is to work through alignment, bone density, cartilage (joint space), distribution and soft tissues. In OA:

• Alignment: malalignment follows cartilage loss; for example a varus knee when the medial compartment narrows.
• Bone density: preserved, often with sclerosis near the joint.
• Cartilage: focal narrowing, osteophytes, cysts.
• Distribution: weight-bearing joints and particular hand joints (below).
• Soft tissues: usually unremarkable; there may be loose bodies or an effusion.

Weight-bearing views are important for the knee. A standing AP (or a flexed weight-bearing PA view) shows true joint space narrowing that a supine film can underestimate. The skyline (axial) view shows the patellofemoral joint, and the lateral shows patellofemoral osteophytes and loose bodies. For the hip, an AP pelvis allows comparison with the other side.

3. Which joints, and where in the joint

Region	Typical pattern
Hand	Distal interphalangeal (DIP) joints, where osteophytes form Heberden's nodes; proximal interphalangeal (PIP) joints, with Bouchard's nodes; and the first carpometacarpal (CMC) joint at the base of the thumb. MCP joints are usually spared in primary OA.
Knee	The medial tibiofemoral compartment is most often affected, with the patellofemoral joint next. Lateral-predominant disease is less common.
Hip	Narrowing is usually superolateral (the femoral head migrates upwards and outwards), sometimes medial. Concentric (uniform) narrowing with axial migration suggests inflammatory arthritis.
Foot	The first metatarsophalangeal (MTP) joint (hallux rigidus) and midfoot joints.
Spine	Facet joint OA and degenerative disc disease (see degenerative spine).

OA in an unusual joint, such as the shoulder, elbow, radiocarpal joint or the second and third MCP joints, should prompt you to consider a secondary cause: previous trauma, avascular necrosis, CPPD (see gout and crystal arthritis), haemochromatosis or a neuropathic joint.

4. Grading severity: Kellgren-Lawrence

The Kellgren-Lawrence (KL) system, first described in 1957, grades radiographic OA from 0 to 4. It is widely used in research and is sometimes quoted in reports or referral criteria. The descriptions below are paraphrased; definitions vary slightly between versions.

Grade	Description
0	No radiographic features of OA.
1	Doubtful: possible small osteophyte, doubtful narrowing.
2	Minimal: definite osteophytes, possible narrowing.
3	Moderate: multiple osteophytes, definite narrowing, some sclerosis, possible deformity of the bone ends.
4	Severe: large osteophytes, marked narrowing, severe sclerosis and definite deformity.

5. Erosive OA and other variants

• Erosive (inflammatory) OA affects the DIP and PIP joints, often in middle-aged women, with episodes of painful swelling. It produces central erosions combined with marginal osteophytes, giving a "gull-wing" outline. This contrasts with the marginal erosions of rheumatoid arthritis and the "pencil-in-cup" of psoriatic arthritis. Ankylosis of the joints may follow.
• Rapidly destructive hip OA is an uncommon pattern in which a hip collapses over months. It can mimic infection, avascular necrosis or a neuropathic joint and usually needs further assessment.
• Secondary OA follows anything that damages a joint: fractures into the joint, previous infection, developmental hip disorders (see the paediatric hip), avascular necrosis and inflammatory arthritis.

6. Do you need an X‑ray at all?

NICE guideline NG226 (2022) advises that OA can be diagnosed clinically without imaging in people aged 45 or over who have activity-related joint pain and either no morning stiffness or morning stiffness lasting no longer than 30 minutes. Imaging is reserved for atypical features, suspected alternative diagnoses, or when it would change management (for example, surgical planning).

Two further points are worth knowing:

• Radiographic severity correlates poorly with symptoms. Some people with severe changes have few symptoms, and some with marked pain have mild changes.
• A normal or near-normal X-ray does not exclude early OA, because cartilage loss and bone marrow changes are seen earlier on MRI.

7. Pitfalls and mimics

• Supine knee films can hide joint space narrowing. Ask for weight-bearing views if joint space matters.
• Calling "OA" in an unusual joint without looking for a cause such as CPPD (chondrocalcinosis), old trauma or avascular necrosis.
• Missing chondrocalcinosis in the menisci or triangular fibrocartilage, which suggests CPPD and changes the differential for an acute hot joint.
• Subchondral cysts versus tumours: large geodes can look like lytic bone lesions. A cyst next to a narrowed joint with OA features is reassuring; a lesion away from the joint, with aggressive features, is not (see bone tumours).
• Hip pain from elsewhere: a painful hip with only mild OA may be due to an occult fracture, avascular necrosis or referred spinal pain. A normal X-ray does not exclude an occult hip fracture (see hip fractures).

Red flags: act now

What to focus on, by role

Role	Priorities
Medical student	LOSS, the hand joints involved, and the contrast between OA and rheumatoid arthritis.
Nurse / practitioner	Know that OA is usually a clinical diagnosis, and recognise the hot joint that needs urgent assessment rather than reassurance.
Junior doctor	Request imaging only when it changes management, use weight-bearing views for the knee, and look for features that do not fit OA.
Radiographer	Weight-bearing knee views where requested and possible, a skyline view for the patellofemoral joint, and true AP pelvis without rotation.
Advanced / FRCR	Erosive OA, rapidly destructive OA, secondary OA patterns and the distribution clues to CPPD and haemochromatosis.

Practise on bone and joint X-rays →

References

1. National Institute for Health and Care Excellence. Osteoarthritis in over 16s: diagnosis and management (NG226). 2022. nice.org.uk
2. Kellgren JH, Lawrence JS. Radiological assessment of osteo-arthrosis. Ann Rheum Dis 1957;16(4):494–502.
3. Radiology Masterclass. Arthritis gallery. radiologymasterclass.co.uk
4. Radiopaedia. Osteoarthritis. radiopaedia.org
5. Royal College of Radiologists. iRefer: making the best use of clinical radiology. irefer.org.uk

For education only. Not a substitute for a formal report, senior review or your local policy. Never use this page to make decisions about a real patient.