Ankle range of motion: normal values

• Dorsiflexion — bringing the top of the foot up towards the shin, as the shin travels over the foot in a squat or a lunge.
• Plantar flexion — pointing the foot down, as when rising onto the toes.
• Inversion and eversion — rolling the sole of the foot in and out, which happens mostly below the ankle joint itself.

Both are measured from neutral — shin upright, foot flat — which is 0° in the clinical convention.

With a goniometer, the pivot sits at the outside of the ankle, one arm along the shin and the other along the side of the foot, and the angle is read from neutral. It can be measured lying down with the foot free, or standing in a lunge with the weight on the foot, and the two give different numbers: compare like with like.

At home, the knee-to-wall lunge is a common stand-in for dorsiflexion: the foot steps back from a wall until the knee can only just touch it, and the distance is recorded. It is a measure in its own right, not an angle.

The ankle angle is made from the knee, the ankle and the toe point (foot_index): the angle at the ankle between the shin and the length of the foot. Shin upright and foot flat reads about 90°.

Filmed side-on with the toes pointing to the right of the picture, bringing the foot up towards the shin closes the angle below 90°, and pointing the foot opens it above 90°. Filmed from the other side the same posture reads as its complement — neutral about 270°, a 20° dorsiflexion 290° rather than 70° — so the figure that matters is the distance from neutral. The ankle is one of the joints Markerless calculates from the landmarks, and every figure and download says so.

On the bike, the cycling view adds the foot's own angle alongside this one: in the indoor cycling example the foot is 10° toe-down at the bottom of the pedal stroke and 39° at the top.

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.

1. Film side-on, the measured foot nearest the camera.
2. Put the camera low, at about ankle or shin height, square to the foot.
3. Keep the knee, ankle and toes in frame — get closer than you would for a whole-body clip.
4. Film barefoot or in a flat, close-fitting shoe; a thick or rockered sole moves the toe point.
5. Decide whether you are measuring standing or not, and do it the same way every time.

The pose model marks the foot with a heel point and a toe point, not the bones of the ankle, so the foot segment is approximate and a bending toe moves it. Inversion and eversion roll the foot about its own length and barely register in a side-on view. Anything out of the filmed plane — a foot turned out towards the camera — reads short.