Range of motion · Hip
Hip range of motion: normal values
Hip range of motion is where video and the clinic most need translating. A goniometer measures the thigh against the pelvis; a camera sees the thigh against the trunk. Here are the published reference values, what Markerless's hip angle actually is, and how to film it so the number means what you think it means.
The movements
- Flexion — bringing the thigh up towards the chest.
- Extension — taking the thigh back behind the body.
- Abduction and adduction — moving the leg out to the side and back in.
- Internal and external rotation — turning the thigh about its own length, which turns the foot in or out.
Reference values
| Motion | Women 20–44 | Men 20–44 | Women 45–69 | Men 45–69 |
|---|---|---|---|---|
| Hip flexion | 133.8° | 130.4° | 130.8° | 127.2° |
| Hip extension | 18.1° | 17.4° | 16.7° | 13.5° |
The study measured flexion and extension at the hip. Abduction and rotation were not part of it, so this page quotes no norm for them.
How it is measured with a goniometer
Usually lying down. For flexion the person lies on their back and the thigh is brought up with the knee bent; for extension they lie face down. The pivot sits at the hip, one arm along the side of the trunk and the other along the thigh. The examiner watches the pelvis, because a pelvis that tips along with the thigh adds movement that is not the hip's.
How Markerless measures the hip
The hip angle is made from the shoulder, the hip and the knee: the angle at the hip between the trunk and the thigh. Standing upright reads 180°, and the distance from 180° is the bend.
Trunk lean is in the number
Because the upper point is the shoulder, not the pelvis, leaning the trunk forwards closes the hip angle exactly as lifting the thigh does. That makes it the right number for a squat, a deadlift or a rowing stroke, where trunk-to-thigh is what a coach watches — and a different number from clinical hip flexion, which is referenced to the pelvis. Read it alongside the low back angle, which shows the trunk's lean on its own.
Side-on, the hip angle shows flexion and extension; extension carries the reading past 180° to the other side. Front-on, the same three points show the leg moving out to the side and back.
Filmed front-on, a person's two sides are mirror images in the picture, so the same movement reads x on one side and 360 − x on the other. The report flips the mirrored side back so left and right sit on the same scale; the downloads keep the engine's own clockwise angles.
How to film it
- Side-on for flexion and extension, front-on for movement out to the side.
- Put the camera at about hip height, square to the person.
- Keep the shoulders, hips and knees in frame for the whole movement.
- Wear fitted clothing at the hips; loose shorts hide where the joint is.
- If you want the hip on its own, keep the trunk as still as the movement allows, and check the low back reading to see how still it stayed.
- Film the same way each time.
What video cannot measure
- Rotation — the thigh turns about its own length, and the three points barely move.
- The pelvis on its own — there are no pelvis landmarks beyond the two hip points, so pelvic tilt cannot be separated from hip movement.
- Movement towards or away from the camera, which reads short.
- The far hip, side-on, when it is hidden behind the near leg.
Questions
What is normal hip range of motion?
In the CDC's reference study, mean hip flexion was 133.8° for women and 130.4° for men aged 20 to 44, and mean hip extension 18.1° and 17.4°. Those were measured with a goniometer, referenced to the pelvis; a video angle that includes trunk lean is a different number.
Can I measure hip range of motion at home?
You can measure the trunk-to-thigh angle from a phone video filmed side-on at hip height, with shoulders, hips and knees in frame. It is the right measure for movements like squats and rowing; it is not a substitute for a pelvis-referenced clinical measurement.
How accurate is a hip range of motion app?
It depends on the app, the joint and above all the filming. Markerless has not published a validation study against a goniometer or marker-based capture, so treat its hip angles as a consistent measure of what the camera saw rather than a clinical absolute. They are strongest for comparing someone with their own earlier clips, filmed the same way.
Does a hip reading outside the reference range mean something is wrong?
No. Reference values are averages from one study's sample, and individuals vary well beyond them. A number from a video is a measurement, not a diagnosis. If movement is painful or has changed, that is a question for a qualified clinician, not for a chart.
References
Soucie, J. M., Wang, C., Forsyth, A., Funk, S., Denny, M., Roach, K. E., Boone, D., & the Hemophilia Treatment Center Network (2011). Range of motion measurements: reference values and a database for comparison studies. Haemophilia, 17(3), 500–507.
The CDC's Normal Joint Range of Motion Study: goniometer measurements of people without conditions affecting joint mobility, published by sex and age group. Every reference value on these pages is copied from its tables.
doi:10.1111/j.1365-2516.2010.02399.x
Gajdosik, R. L., & Bohannon, R. W. (1987). Clinical measurement of range of motion. Physical Therapy, 67(12), 1867–1872.
A review of goniometry with the emphasis on its reliability and validity: a goniometer reading is itself a measurement with its own error, not a ground truth to compare everything else against.
doi:10.1093/ptj/67.12.1867
Keogh, J. W. L., Cox, A., Anderson, S., Liew, B., Olsen, A., Schram, B., et al. (2019). Reliability and validity of clinically accessible smartphone applications to measure joint range of motion: A systematic review. PLOS ONE, 14(5), e0215806.
A systematic review of how smartphone apps for measuring joint range of motion have been tested for reliability and validity — the place to start if you are choosing one.
doi:10.1371/journal.pone.0215806