Video Gait Analysis or 3D Skeletal Imaging: What Is the Difference?
Video gait analysis records how you move, usually on a treadmill, and shows muscle timing, stride pattern and foot strike. 3D skeletal imaging, such as a standing EOS scan, captures the actual shape and alignment of your bones under load. One watches movement. The other reveals the structure behind it. They answer different questions and often work best together.
Key takeaways
- Video gait analysis shows how your body moves in real time, but it films the skin surface, not the skeleton.
- 3D skeletal imaging (EOS) captures exact bone geometry and joint alignment while you stand weight-bearing.
- Skin markers can shift during movement, which limits the precision of video-based measurements.
- Both tests are complementary. Movement data explains the "how," skeletal data explains the "why."
- Neither replaces MRI when soft tissue, disc or nerve detail is needed.
What is video gait analysis and what does it show?
Video gait analysis is a movement assessment. A camera, sometimes several cameras, records you walking or running, often on a treadmill. A clinician or software then reviews the footage frame by frame. It shows stride length, cadence, foot strike pattern, knee tracking and how your pelvis, trunk and arms move through each step.
Many running shops, physiotherapy clinics and sports medicine centres offer treadmill gait analysis. It is useful for spotting compensations, timing faults and asymmetry in your movement. Some labs add pressure plates or force sensors to measure ground reaction forces.
What is 3D skeletal imaging?
3D skeletal imaging creates a precise, measurable picture of your bones and joints. An EOS scan, for example, takes a full-length image from head to foot while you stand naturally. Because you are upright and weight-bearing, the image shows how gravity and your own body weight affect your skeleton. A specialist can then measure bone length, joint angles, rotation and overall lower limb alignment from the resulting 3D reconstruction.
How does video gait analysis compare with 3D skeletal imaging?
The two tests measure fundamentally different things. The table below summarises the key differences.
| Feature | Video gait analysis | 3D skeletal imaging (EOS) |
|---|---|---|
| What it captures | Surface movement patterns during walking or running | Bone shape, length, rotation and joint alignment |
| Position | Moving on a treadmill or walkway | Standing still, full weight-bearing |
| Static vs dynamic | Dynamic (in motion) | Static (standing alignment under load) |
| Markers | Skin markers or markerless camera tracking | No markers needed. Bones are imaged directly. |
| Measurement basis | Estimated joint centres from skin surface | True bone geometry from calibrated radiograph |
| Radiation | None | About 90% less radiation than a standard X-ray, around ten times less |
| Soft tissue detail | None (external view only) | Bones and joints only. MRI is better for soft tissue. |
| Best for | Identifying movement faults, running technique, shoe selection | Diagnosing structural causes such as leg-length difference, torsion, joint malalignment |
Why can video gait analysis miss structural problems?
Video gait analysis is valuable, but it has limitations that are worth understanding. It records what happens on the outside of the body. It cannot see bones, joint surfaces or internal rotation.
These limitations do not make video gait analysis wrong. They simply mean it answers a different question. It tells you how you move. It does not tell you why your skeleton is shaped the way it is.
How does standing EOS imaging add to a gait assessment?
An EOS scan images your entire skeleton from head to foot while you stand. Because your muscles, joints and gravity are all active, the image shows your real, loaded alignment. Lying-down scans relax the body and can mask problems that only appear when you are upright.
Your body is a connected chain. A twist in the shinbone can change how the knee tracks, which shifts the hip, which tilts the pelvis. If you only look at one joint, you may see the compensation but miss the cause. A full-length standing image captures the whole chain in a single view, giving clinicians EOS compared with x-ray, CT and MRI context they cannot get from traditional imaging alone.
Understanding your postural sway and static alignment alongside your dynamic movement data gives the fullest picture. The gait video shows the movement fault. The skeletal image shows the structural reason behind it.
Want to understand what your skeleton looks like under load? At ScanAlign, standing EOS imaging in London, a standing whole-body scan takes about 20 seconds.
Book a free video consultationWhen should you choose gait analysis, skeletal imaging, or both?
This depends on your question. If you want to improve running form or check shoe fit, a video gait assessment may be all you need. If you have a persistent structural concern, such as a leg that feels longer, a knee that keeps giving way, or recurrent hip pain after years of physiotherapy, then skeletal imaging can reveal what is happening at bone level.
- Want to improve running or walking technique
- Need help choosing the right footwear
- Want to see how muscles fire during movement
- Have a sports coach or physiotherapist guiding training
- Have ongoing pain that has not responded to treatment
- Suspect a leg-length difference or bone rotation issue
- Need pre-surgical alignment measurements
- Want to understand why a gait pattern is abnormal, not just that it is
Many people benefit from both. A physiotherapist reviews the gait data, a radiologist reviews the skeletal data, and together they build a clearer picture. You can book a skeletal alignment scan without a GP referral.
When MRI is the better choice: EOS shows bones, joints and alignment. For soft tissue, discs or nerves, MRI is usually the better tool. If your clinician suspects a ligament tear, cartilage damage or nerve compression, an MRI is likely more appropriate than either gait analysis or skeletal imaging.
Frequently asked questions
Video gait analysis is designed to assess movement patterns, not bone structure. It can highlight abnormal motion, but it cannot diagnose conditions like bone torsion, leg-length differences or joint deformity. For those, you need imaging that shows the skeleton directly.
It typically measures stride length, cadence, foot strike angle, knee tracking and pelvic movement during walking or running. Some systems also record ground reaction forces through a pressure plate beneath the treadmill belt.
An EOS scan images your entire body from head to foot in a single upright pass with about 90% less radiation than a standard X-ray, around ten times less. It also produces a 3D model of your skeleton, which a standard X-ray cannot do.
No. ScanAlign is a self-pay clinic and you can book directly without a GP or specialist referral. Your first step is a free video consultation to check the scan is right for you.
Yes. The two tests are complementary. Many clinicians recommend combining movement data from a gait lab with structural data from a standing skeletal scan for the most complete picture.
Skin markers are small reflective dots placed on landmarks like the knee or ankle. As the body moves, the skin and underlying soft tissue shift, which moves the marker away from the actual bone position. This is called soft tissue artefact and it can introduce measurement errors in video-based analysis.
Gait analysis costs vary widely depending on the clinic and the technology used. For EOS scan pricing at ScanAlign, please visit the FAQs and cost page.
An EOS scan uses about 90% less radiation than a standard X-ray, around ten times less. The dose is very low. Your radiographer will explain the details during your consultation.
It may show that your knee collapses inward during your stride, which is useful. But it cannot tell you whether that movement is caused by muscle weakness, bone rotation, or a joint alignment issue. If the problem persists, imaging of the skeleton may help find the structural cause.
Sudden leg weakness, numbness or loss of bladder or bowel control can indicate a serious condition that needs urgent attention. Please contact your GP, call 111, or go to A&E rather than booking an imaging appointment.
See the structure behind the movement
A free video consultation helps you find out whether a standing skeletal scan is the right next step for your concern.
Book a free video consultationWritten by Abbas Dhami (Specialist Diagnostic Radiographer)
Sources
- Leardini A, Chiari L, Della Croce U, Cappozzo A. Human movement analysis using stereophotogrammetry. Part 3: Soft tissue artifact assessment and compensation. Gait & Posture. 2005;21(2):212-225.
- Illés T, Somoskeöy S. The EOS imaging system and its uses in daily orthopaedic practice. International Orthopaedics (SICOT). 2012;36(7):1375-1386.
- Royal College of Radiologists. iRefer: Making the best use of clinical radiology. Available at: irefer.org.uk.
This page is general information and not a diagnosis.
ScanAlign is the trading name of CoreMed Solutions Ltd and operates under The Harley Street Hospital's CQC licence.