Reading your baby's hip ultrasound: Graf types I to IV explained
Written by Dr. Mutasem Aldhoon, pediatric orthopedic consultant · Medically reviewed by the Baby Hip Center pediatric orthopedic team · Last reviewed September 1, 2026
The Graf classification grades how well your baby's hip socket has formed, from type I (normal) to type IV (fully dislocated). Types I and IIa usually need nothing more than a repeat scan. Type IIb and above normally means treatment, most often a Pavlik harness. The type on its own does not decide the plan — your baby's age matters just as much.
If your baby's ultrasound report says "Graf type IIa" or "type III", you have probably already searched for what it means and found either a blank medical definition or nothing at all. This page explains each type in plain language, and what it usually means for what happens next.
What the Graf method actually measures
On a hip ultrasound the sonographer finds a standard side-on view of the hip and draws three lines: along the wall of the pelvis, along the bony roof of the socket, and along the cartilage rim. From those lines come two numbers — the alpha angle (how deep and well formed the bony socket is) and the beta angle (how the cartilage rim is sitting). The Graf type is the label given to that combination, together with whether the ball of the hip is centred, pushed to the edge, or out of the socket entirely.
The Graf types, one by one
| Type | Alpha angle | What it means | Usual plan |
|---|---|---|---|
| I | 60° or more | A mature, normal hip. The ball sits deep in a well-formed socket. | No treatment. No repeat scan needed. |
| IIa | 50-59°, under 12 weeks old | Immature rather than abnormal — the socket is simply still developing. | Repeat scan in about 4-6 weeks. Most become type I on their own. |
| IIb | 50-59°, over 12 weeks old | The same shape, but now late. It is no longer catching up by itself. | Treatment, usually a harness or abduction brace. |
| IIc | 43-49° | A severely shallow socket. The ball is still in place but only just. | Treatment, and close follow-up because it can slip. |
| D | 43-49°, ball beginning to slip | Decentring: the head is starting to move out of the socket. | Treatment now, urgently. |
| III | under 43° | Dislocated. The head is out of the socket, and the cartilage rim is pushed upwards. | Treatment, often with a period of closer monitoring or reduction. |
| IV | under 43° | Dislocated, with the cartilage rim pushed down into the joint. | Specialist treatment; harness alone may not be enough. |
Type IIa is not a diagnosis of hip dysplasia
This is the single biggest cause of parental panic we see. In a baby under 12 weeks, a slightly shallow socket is often just an immature socket. The scan is repeated precisely because most of these hips are normal by the next visit.
Why your baby's age changes everything
The very same alpha angle of 55° means "still developing, check again" at 4 weeks old and "needs treatment" at 16 weeks old. Sockets deepen fastest in the first three months, and the window in which a simple harness works well closes at around six months. That is why reports always state the age in weeks, and why a scan result read without the age attached is close to meaningless.
What to ask at your next appointment
- What was the alpha angle on each side, and what was my baby's exact age in weeks at the scan?
- Is the head of the femur centred, decentred, or dislocated?
- Is this the first scan, or is it a comparison — and did the angle improve or worsen?
- If we are watching and waiting, when exactly is the repeat scan, and who books it?
- If treatment is starting, what is the plan if the first scan in the harness does not show improvement?
Common wording on reports, translated
| What the report says | What it means |
|---|---|
| Physiologically immature hip | Shallow but age-appropriate — usually a repeat scan |
| Mature hip / Graf I | Normal, nothing further needed |
| Subluxatable / decentred | The ball can be pushed partly out of the socket |
| Dislocated / luxated | The ball sits outside the socket |
| Cartilaginous roof deformed | The soft rim of the socket has been pushed out of shape |
If you have the images themselves — the printed sheet or a disc from the hospital — those numbers can be checked. A report can be transcribed wrongly, the standard view can be off-plane, and an angle measured on a poorly positioned image will read lower than the hip truly is.
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Read next
- What the alpha angle on a hip ultrasound means
The alpha angle measures how well formed your baby's hip socket is. Here is what a normal value looks like, and what a low number means at each age.
- The Ortolani and Barlow tests, explained for parents
What the doctor is feeling for during the newborn hip examination, what a positive Ortolani or Barlow means, and why the tests stop working after about 3 months.
- Hip ultrasound or X-ray: which one does your baby need?
Ultrasound is used up to about 4-6 months, X-ray after that. Why the cut-off exists, what each test shows, and what radiation exposure really means here.
This page is general information about developmental dysplasia of the hip, not a diagnosis of your own baby. It does not replace examination by your baby's doctor, and it is not for emergencies.