Running gait video analysis for physios and clinicians

Caden is a consumer iPhone app that does 2D running gait analysis from a phone clip. For a physiotherapist it is a quick screen in the corridor and a homework tool the patient runs at home between visits. It is not a gait lab. No force plates, no 3D, no pressure mat, and the pose model is a general one, not a validated clinical instrument. Read it as a repeatable 2D observation with numbers attached.

What it measures

From a side view, filmed at hip height 6 to 8 metres from the runner, Caden reports:

• Where your foot lands. landing reach, the horizontal distance from hip to landing ankle at initial contact, as a fraction of leg length.
• Upper body lean. Trunk lean in degrees from vertical.
• Knee bend on landing. Knee flexion at midstance.
• Knee bend at push-off. Knee flexion of the swing leg in recovery.
• Arm bend. Elbow angle.
• Head position. Neck offset in degrees.
• Cadence. Steps per minute.

Caden currently films from the side only. For frontal-plane signs like hip drop or knee valgus, film your own front or behind clip and eyeball it. The app does not analyse those views.

Each clip gets a form score out of 100 and Breakpoints, which are freeze frames at initial contact, midstance and toe-off with a skeleton overlay and the metrics for that phase. The app removes the audio track and uploads the clip privately to the patient's account, where pose estimation runs on Caden's servers. Deleting the analysis removes the stored media.

What it does not measure

Say this to patients before they ask. Caden cannot measure:

• Ground reaction force, loading rate or contact time.
• Hip drop, hip or pelvic rotation, or pelvic tilt in the frontal plane.
• Pronation, rearfoot angle or foot pressure.
• Leg length difference.
• Anything under load in a clinic sense. It is video.

The measures have not been validated against a motion capture system in a published study, and the site does not claim otherwise. Treat between-clip changes in the same runner, same view, same setup as more meaningful than any absolute value.

Where it is useful in a clinic

As a quick screen. A patient runs past a phone in the car park at easy pace. In under a minute you have landing reach, trunk lean, knee flexion at midstance and cadence, with a foot strike freeze frame you can show them. It is faster than scrubbing a slow-motion video by hand, and the numbers are the same each time you use it.

As homework. The patient films at home every four weeks with the same setup. Stats keeps every clip and trends each metric. Before and after compares any clip against the baseline. You see whether the landing reach you cued in clinic has changed on their own roads, when you are not watching.

As a way to explain. The coach's tip narrates results in plain language with one cue per metric. Patients understand "your foot lands ahead of your hip" faster than a joint angle. The plain words are there for that reason. See how to film yourself running for the setup instructions to give patients.

A sample 4-week home plan

Caden builds a 4 or 8 week plan on the Exercises tab from the patient's lowest metrics, three short sessions a week at a session length the patient chooses. The exercise pool is small and general. Running drills are A-march, A-skip and quick-feet strides. Strength is slow calf raises, glute bridge, split squat and step-ups. Balance is single-leg balance. Core is dead bug. Mobility is hip flexor stretch and ankle rocks.

For a patient whose landing reach is the lowest score, the plan is A-march, slow calf raises and single-leg balance in weeks 1 and 2, then A-skip, quick-feet strides and glute bridge in weeks 3 and 4, with one cue on easy runs.

Short, quiet steps.

The plan is not clinical. Replace it with your own programme and use the app only for measurement if that fits the patient better.

What Caden will not do for a clinician

There is no clinician dashboard or multi-patient account. Each patient owns their own data and shares screenshots or frames with you.

It does not export raw joint coordinates or a CSV.

It does not make or support a diagnosis. The app text says "may help" and "often linked with", never more. Please keep the same language when you show it to patients.

How to do it in Caden

1. Ask the patient to install Caden on their iPhone and tap Run a new analysis.
2. Phone at hip height 6 to 8 metres from the path, filming side on, 10 to 20 seconds at easy pace.
3. On the results screen, read the Where your foot lands, Knee bend on landing and Upper body lean dials and cadence.
4. Tap Breakpoints, then Foot strike and Midstance, to show the patient the frames.
5. For frontal-plane signs like hip drop, film your own front or behind clip and review it by eye. Caden does not analyse that view.
6. Set a four-week re-film. Open Before and after in Stats at the next visit.

FAQ

Is Caden a clinical gait analysis tool?

No. It is a consumer app that gives 2D measures from a phone video. Use it as a screen and a homework tracker. A gait lab with force plates and 3D capture is a different tool.

How accurate are the angles?

They come from a general pose model, with no published validation against motion capture. Same runner, same view, same setup gives repeatable numbers. Compare clips against each other rather than against a clinical norm.

Can patients share their results with me?

Yes, by screenshot or by sharing the annotated frames. The frames stay stored with the analysis under the patient's account until they delete it. There is no clinician login.

Does it measure pronation or knee valgus?

No. Caden analyses the side view only. Hip line, pronation and valgus angles need a different tool or a clinician's eye on frontal footage.