Goniometer: Joint Angle & ROM

Goniometer is a joint angle meter: place the phone on the limb and read how many degrees a joint moves, from a start position you set yourself. Use it for knee, elbow, shoulder, hip, ankle, wrist and neck flexion, and keep every saved result in one place to follow your range of motion (ROM) over the weeks.

HOW A MEASUREMENT WORKS

1. Pick the joint. A placement line tells you where the phone goes: flat on the limb, long edge along it, screen facing out.
2. Hold the start position still and tap Set start. That position becomes 0°.
3. Move to the end of the motion and hold still. After about three seconds the end is marked automatically — a ring fills while you hold and a haptic confirms the mark. You can also tap Mark end at any time.
4. Check the number and tap Save. The recorded range is the largest marked angle minus the smallest, including the start.

The app waits for a steady reading before it lets you set the start or mark an end, so a fast swing is not recorded half-way. If the phone is placed on its side, where the angle cannot be read reliably, it asks you to reposition instead of showing a wrong number. Sweeps past 180° keep counting instead of wrapping around.

WHAT YOU GET

• Live angle from your start position, on a clear dial with 45° marks.
• Automatic end marking plus a manual Mark end button.
• Eight motions: knee, elbow, shoulder, hip and neck flexion, wrist flexion and extension, and the ankle (dorsiflexion and plantarflexion together).
• Your result as a percentage of the AAOS reference range, with the published source one tap away.
• Left and right tags, with the difference to your latest measurement on the other side.
• Progress tab: every saved measurement per joint with latest, largest and record count.
• CSV export of your history, and a simple 0–10 pain log.
• A reference table and a step-by-step guide with accuracy tips.

WHO IT'S FOR

People following a rehab or stretching plan who want to see their range change over weeks, trainers and coaches checking mobility, and anyone curious how far a joint moves.

GOOD TO KNOW

The app measures movement in a vertical plane; keep the other body segment still. Readings depend on phone placement and case. Goniometer is not a medical device and does not diagnose, treat or prevent any condition. Talk to a healthcare professional about your results.