The paediatric elbow X-ray

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

The child's elbow is one of the most feared films in emergency medicine. Up to six ossification centres appear at different ages, the fractures are often subtle, and the important ones can damage the brachial artery or the nerves of the forearm. The good news is that a short, fixed routine finds nearly all significant injuries: check the view → fat pads → anterior humeral line → radiocapitellar line → ossification centres (CRITOE) → cortices. This page teaches that routine and the injuries it is designed to catch.

1. Is the lateral a true lateral?

The standard series is an AP with the elbow extended and a lateral with the elbow flexed to 90°. An injured child often cannot straighten the arm, so the AP may be taken in partial flexion and look odd. That is acceptable, but the lateral has to be right, because most of the key signs are read from it.

• On a true lateral, the distal humerus forms an hourglass or figure-of-eight shape, and the capitellum and trochlea overlap as concentric circles.
• If the humerus is rotated, the anterior humeral line and fat pads become unreliable. If the film is clearly rotated and the child is distressed, ask whether a repeat would change management before requesting one.
• Oblique views can help with a suspected lateral condyle fracture, which is often subtle on the AP.

2. Fat pads

Two pads of fat lie just outside the joint capsule. When the joint fills with fluid or blood, they are pushed outwards, and fat shows as a dark (lucent) shape against the grey soft tissue.

Fat pad	Normal	Abnormal
Anterior	Often visible as a thin, flat lucent strip lying along the front of the humerus.	Lifted away from the bone into a triangle: the sail sign.
Posterior	Not visible on a true lateral at 90°, because it sits deep in the olecranon fossa.	Any visible posterior fat pad is abnormal. It indicates an effusion.

After trauma, an effusion with no visible fracture line should be treated as an occult fracture. In a child the most likely culprit is a supracondylar fracture; in an adult it is a radial head fracture (see elbow fractures). Management is usually immobilisation and clinical review according to local protocol.

3. The two lines

Anterior humeral line

On the lateral, draw a line down the anterior cortex of the humerus and extend it through the capitellum. It should pass through the middle third of the capitellum. If it passes through the anterior third, or misses the capitellum altogether, the capitellum has moved backwards. That is the hallmark of an extension-type supracondylar fracture.

The rule is less reliable in very young children. Under about 4 years, the capitellum is small and the line may normally pass through its anterior third (Radiopaedia; Radiology Masterclass). Use it together with the fat pads and the clinical picture.

Radiocapitellar line

Draw a line along the long axis of the radial neck and shaft. It should pass through the capitellum on every view, whatever the position of the elbow. If it does not, the radial head is dislocated. An isolated radial head dislocation is rare in children, so look hard at the ulna for a fracture or plastic bowing: this is the Monteggia pattern, and it is easily missed. See Monteggia and Galeazzi injuries.

4. Ossification centres: CRITOE

The secondary ossification centres of the elbow appear in a fairly reliable order. The ages below are approximate and vary between sources by about 1–2 years. Girls tend to be earlier than boys. Some texts give 1-3-5-7-9-11 years; others use slightly different values.

Order	Centre	Approximate age of appearance (years)
C	Capitellum	1
R	Radial head	3
I	Internal (medial) epicondyle	5
T	Trochlea	7
O	Olecranon	9
E	External (lateral) epicondyle	11

Exact ages matter less than the order. The key rule is that the trochlea should not be ossified before the internal (medial) epicondyle. If you see an ossified fragment in the position of the trochlea but no medial epicondyle in its normal place on the AP, suspect that the medial epicondyle has been avulsed and is trapped in the joint. This is easy to mistake for a normal trochlear centre.

5. Supracondylar fractures and Gartland

The supracondylar fracture of the distal humerus is the most common elbow fracture in children, around 60% in the curriculum sources, typically between about 3 and 10 years. It usually follows a fall on an outstretched hand with the elbow hyperextended. About 95% are extension type, with the distal fragment displaced backwards; flexion types are uncommon.

Signs

• Raised anterior fat pad (sail sign) and a visible posterior fat pad.
• Anterior humeral line passing in front of the middle third of the capitellum.
• A transverse lucency or cortical buckle just above the condyles, often best seen on the lateral.
• Altered Baumann's angle on the AP compared with the other side (varus tilt).

Gartland classification (extension type)

Type	Appearance
I	Undisplaced. There may be only a fat pad sign or a subtle cortical break. The anterior humeral line is usually normal.
II	Displaced (angulated), but the posterior cortex is intact and acts as a hinge.
III	Completely displaced, with no cortical contact.
(IV)	Unstable in both flexion and extension: a modification that is usually recognised under anaesthesia rather than on the X-ray.

Why they matter

A displaced fracture can injure the brachial artery (a pale or pulseless hand) or nerves: the anterior interosseous nerve is the most often affected, followed by the radial and ulnar nerves. Other complications are compartment syndrome (with Volkmann's ischaemic contracture if missed) and cubitus varus ("gunstock" deformity) after malunion.

6. Other injuries: condyle, epicondyle, radial neck

• Lateral condyle fracture: the second most common. A line runs from the lateral metaphysis into the capitellum. It is often subtle on the AP, and an internal oblique view helps. It behaves like a Salter-Harris type IV injury (see Salter-Harris fractures) and is unstable, with a high risk of non-union and later cubitus valgus (with tardy ulnar nerve palsy). Even small displacement usually needs orthopaedic review.
• Medial epicondyle avulsion: seen in older children and adolescents, with throwing injuries and especially after an elbow dislocation. The fragment may be displaced only slightly, or may be entrapped in the joint (apply the CRITOE rule).
• Radial neck fracture: in children the radial neck tends to fracture, rather than the radial head as in adults. Look for angulation or a buckle of the neck on both views.
• Elbow dislocation: usually posterior. Check for an associated medial epicondyle fracture before and after reduction.
• Pulled elbow (nursemaid's elbow): subluxation of the radial head under the annular ligament in a toddler after a pull on the arm. The X-ray is normal, and imaging is not needed for a typical history and examination.

7. Pitfalls and mimics

• Ossification centres mistaken for fractures, and fractures mistaken for centres. A normal centre is rounded and has a smooth, corticated edge in the expected place for the child's age. A fragment is often irregular, angular or in the wrong place.
• The medial epicondyle centre can look fragmented as a normal variant. Use the clinical findings and, if needed, a comparison view.
• Rotated lateral films make the anterior humeral line meaningless. Judge the film quality first (see image quality).
• Stopping at the supracondylar fracture: combined injuries happen. Check the radial neck, the condyles and the radiocapitellar line every time.
• Pattern and history: elbow fractures in a pre-mobile infant, or an inconsistent history, should prompt a safeguarding assessment. See non-accidental injury.

Red flags: act now

What to focus on, by role

Role	Priorities
Medical student	CRITOE, the two fat pads and the two lines. Know that a visible posterior fat pad is abnormal and that supracondylar fractures are the most common injury.
Nurse / ENP	Neurovascular checks before and after splinting, and escalation of a pale hand or rising pain. Pulled elbow needs no X-ray if the story and examination are typical.
Junior doctor	Apply the full system every time, look for Monteggia on forearm films, document neurovascular status and refer Gartland II/III and lateral condyle injuries promptly.
Radiographer	A true 90° lateral is the most important image. Consider an oblique view if the protocol allows and the lateral condyle is in question.
Advanced / FRCR	Entrapped medial epicondyle, minimally displaced lateral condyle fractures, Baumann's angle and flexion-type injuries.

Practise on paediatric X-rays →

References

1. Radiology Masterclass. Paediatric elbow. radiologymasterclass.co.uk
2. Radiology Masterclass. Elbow X-ray gallery. radiologymasterclass.co.uk
3. Don't Forget the Bubbles. Supracondylar fractures. dontforgetthebubbles.com
4. Radiopaedia. Monteggia fracture-dislocation. radiopaedia.org
5. Radiopaedia. Salter-Harris classification. radiopaedia.org
6. British Orthopaedic Association. BOAST guidance. boa.ac.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.