How to read a skeletal X‑ray

Written by the X-Ray Atlas editorial team from the sources listed below · Medical review pending · Updated 25 October 2026 · Level: Beginner

Bone and joint films are among the most common X-rays requested in emergency departments and minor injury units, and they are often first read by the clinician who ordered them. Most missed fractures are not invisible. They are missed because the reader looked at one view, followed one bone, found nothing obvious and stopped. A fixed system, used the same way on every film, prevents that. This page teaches a widely used sequence, ABCS: Adequacy (and alignment), Bone, Cartilage and joints, Soft tissues, followed by a check of the areas where injuries hide.

1. Before you look

• Right patient, right film, right side. Check the name, identifier, date and time. The skeleton is symmetrical, so the side marker matters more than on almost any other film. A wrong-side film of a normal limb looks perfectly normal.
• The clinical question. Where exactly is the tenderness? What was the mechanism? A film is read far better when you know which bone the patient is pointing to. "Treat the patient and not the X-ray" is a teaching principle repeated in the Radiology Masterclass tutorials for good reason.
• Was imaging indicated? For many injuries a clinical decision rule decides this. See clinical decision rules.
• Old films. Previous imaging is described as the cheapest test in radiology. It can show that a "new" lesion is long-standing, or reveal a lytic lesion that turns a minor-trauma fracture into a pathological one.

2. A: adequacy and views

Two views at right angles. In trauma at least two views are usually needed, typically an AP and a lateral taken orthogonally to each other. A fracture can be almost invisible on one view and obvious on the other: the classic example is a distal fibular fracture that shows as a trivial cortical irregularity on the AP ankle and a clear oblique line on the lateral. Some regions need more than two views as standard, for example dedicated scaphoid views, a mortise view at the ankle, or inlet and outlet views of the pelvis. See X-ray projections.

Coverage. The film must include the whole area of concern. For a long-bone injury, the joint above and the joint below should be imaged, because force travels along the bone and injuries occur in patterns: a proximal fibular fracture with an ankle injury (the Maisonneuve pattern) is the textbook example.

Exposure and positioning. A good exposure lets you see the cortex clearly and tell cortex from medulla without effort. A poorly positioned film can hide a fracture or create a false one, and jewellery or dressings can obscure the bone entirely. If the image is not good enough to answer the question, say so, ask the radiographer about technical limits and request a repeat if it is clinically justified. Image quality principles are covered in image quality: RIPE.

3. A: alignment

Before looking at fine detail, step back and check that the bones line up with each other at every joint on both views. Loss of alignment may indicate a fracture, a dislocation (no contact between the articular surfaces) or a subluxation (partial contact), and these are often linked to soft-tissue and ligament injury.

Many regions have their own alignment lines that make this objective. Examples covered in the region modules include the anterior humeral and radiocapitellar lines at the elbow, Shenton's line at the hip and the four lines of the cervical spine. Learn them region by region in paediatric elbow, hip fractures, cervical spine and foot fractures.

4. B: bone, cortex and texture

Trace every cortex. Follow the outline of each bone on each view, all the way round, including bones at the edge of the film that are not the "target". The normal cortex is a smooth, continuous white line. A fracture usually shows as a lucent line that runs through cortex and medulla and can be traced from one cortex towards the other, often with a step or break in the outline. An impacted fracture, where the bone ends are driven into each other, can be subtle, so do not rely on seeing a lucent line.

Look at the texture. Inside the cortex, the fine trabecular pattern should be continuous. A subtle disruption or sudden change in that pattern can be the only sign of an undisplaced fracture, for example in the femoral neck, where comparison with the other hip can help.

Assess bone density and focal lesions. Thin cortices and generally reduced density suggest osteopenia. A focal area that is darker (lytic), whiter (sclerotic) or mixed should be described by its site and margins. A fracture through such a lesion, or after trivial trauma, should prompt the question "is this pathological?". See bone tumours and metabolic bone disease.

Describe what you find in a structured way: bone, site (diaphysis, metaphysis, epiphysis; intra- or extra-articular), pattern, and displacement in at least two planes. The full vocabulary is in how to describe a fracture.

5. C: cartilage and joint spaces

Articular cartilage does not show on X-ray, so it is assessed indirectly by the joint space. Look at each joint on each view:

• Congruity: do the articular surfaces match and sit evenly? A step in an articular surface suggests an intra-articular fracture.
• Width: narrowing can reflect cartilage loss; widening can reflect dislocation, ligament disruption or dissociation between bones (for example in the carpus).
• Degenerative change: joint space narrowing, osteophytes, subchondral sclerosis and subchondral cysts point to osteoarthritis. Erosions are a feature of inflammatory arthritis such as rheumatoid arthritis: see inflammatory arthritis.

6. S: soft tissues

Abnormal soft tissue can be more obvious than the bone injury, and can be the only clue to a fracture that is not visible. Check for:

• Swelling over a specific bone, which directs your search.
• Joint effusion. Fluid itself has the same density as muscle, so an effusion is inferred from displaced fat. At the elbow, the anterior fat pad is normally a thin line along the humerus and the posterior fat pad is hidden in the olecranon fossa. A raised anterior fat pad (the "sail sign") or any visible posterior fat pad on a lateral film indicates an effusion. After trauma this usually means an occult fracture: most often the radial head in adults and a non-displaced supracondylar fracture in children. See elbow fractures.
• Fat–fluid level (lipohaemarthrosis). Fat and blood from the marrow leak into a joint through an intra-articular fracture. Because fat floats on blood, a straight horizontal line appears, but only on a horizontal-beam image (at the knee, a cross-table lateral). It is most common at the knee, typically with a tibial plateau or distal femoral fracture. Its absence does not exclude a fracture. See knee fractures.
• Gas in the soft tissues, suggesting an open wound or, in the right setting, infection.
• Foreign bodies such as glass or metal. See foreign bodies.

7. Second look, comparison and next steps

• Keep looking after the first finding. Injuries come in patterns, and finding one abnormality makes it easier to miss a second (satisfaction of search). Check every bone on every image.
• Compare. With the other side when it has been imaged (the hips on a pelvis film are a built-in comparison), and with old films.
• Know when the X-ray is not enough. Some fractures are occult on the first film. NICE recommends MRI when a hip fracture is suspected despite negative hip X-rays of an adequate standard (CT if MRI is not available within 24 hours or is contraindicated), and suggests considering MRI as first-line imaging for a suspected scaphoid fracture after a thorough examination. Follow-up films may also show a healing fracture, as periosteal new bone appears.
• Get a definitive report. NICE NG38 recommends that a trained reporter delivers the definitive written report of emergency department X-rays for suspected fractures before the patient is discharged. Your own reading is a preliminary interpretation, not a replacement for it.

8. Pitfalls

• One view only. Never clear a bone on a single projection in trauma.
• Looking only where it hurts. The fracture may be at the joint above or below, or the pain may be referred from elsewhere.
• Mistaking a variant for a fracture (or the reverse). Compare sides and use reference images.
• A normal film does not exclude a fracture when the clinical findings are strong. Treat the patient, and follow local pathways for suspected occult fractures.

Red flags: act now

What to focus on, by role

Role	Priorities
Medical student	Say ABCS aloud on every film. Learn two views, the joint above and below, and the elbow fat pads.
Nurse / ENP	Match the film to the point of tenderness, check both views, and recognise effusion and lipohaemarthrosis as signs of a hidden fracture. Know your local process for preliminary interpretation and recall.
Junior doctor	Trace every cortex on every view, compare with old films, and know when to request MRI or CT for a suspected occult fracture. Document your interpretation.
Radiographer	Adequacy, coverage and extra views; horizontal-beam laterals when a lipohaemarthrosis is possible; preliminary clinical evaluation of obvious acute findings.
Advanced / FRCR	Region-specific alignment lines, normal variants, pathological fractures and injury patterns at speed.

Practise on upper limb X-rays → Lower limb →

Unfamiliar term? See the glossary.

References

1. Laubscher M, Held M, McCollum G. Approach to orthopaedic X-rays. In: Orthopaedics for the primary care practitioner. University of Cape Town Open Books. openbooks.uct.ac.za
2. University of Saskatchewan. Approach to bone and joint X-rays. In: Undergraduate Diagnostic Imaging Fundamentals. openpress.usask.ca
3. Radiology Masterclass. Musculoskeletal X-ray: systematic approach and viewing principles. systematic approach; viewing principles
4. Skaggs DL, Mirzayan R. The posterior fat pad sign in association with occult fracture of the elbow in children. J Bone Joint Surg Am 1999;81(10):1429–33. doi:10.2106/00004623-199910000-00007
5. Radiopaedia. Elbow joint effusion; Lipohaemarthrosis. elbow effusion; lipohaemarthrosis
6. O'Keeffe D, Nicholson DA, Driscoll PA, Marsh D. ABC of emergency radiology: the ankle. BMJ 1994;308:331 (normal variants such as the os trigonum). pmc.ncbi.nlm.nih.gov
7. NICE. Fractures (non-complex): assessment and management (NG38). nice.org.uk
8. NICE. Hip fracture: management (CG124). nice.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.