Your recovery log

The knee bend, measured on your leg.

One movement, measured the same way every time, so the number means something next week. Your phone's tilt sensor reads the slope of your thigh, then of your shin; the knee bend is the two added together. No camera, no guessing from a picture.

Kept on this device only. The tilt readings are used on this phone and saved here. Nothing is uploaded. You can delete all of it on your summary page.

Back to your log Summary for your care team

How to take the reading

Sit on a chair with your feet flat, or lie on your back. Slide the heel of the leg you are measuring back toward you as far as it comfortably goes, and hold it there for the two readings.

  1. Lay the phone flat on top of your thigh, the top of the phone toward your knee, screen facing away from the leg. Hold still for a second and it reads itself.
  2. Hold the phone flat against the front of your shin, the same way: top toward the knee, screen facing away from the leg. Hold still again; it reads the second number.
  3. Read the bend. Save it if the phone sat flat on the leg both times; redo it if it slipped. Two taps in all: Start, then Save.
Ask first. After an operation, check with your surgeon or physical therapist before you push the bend. Slide to where it is comfortable, not to where it hurts, and stop if it does.

Which knee?

Take the reading

–tilt, in degrees

Tap Start. Your phone may ask for permission to use its motion sensor; it is read on the phone and nothing leaves.

Your readings

No readings yet. Your first one is the number everything after it is compared with.

What this is, and what it is not

It is a tilt measurement, the same physics as the inclinometer apps some clinics use. A phone's tilt sensor has been compared with a long-arm clinic goniometer for knee angles: in five volunteers the two agreed to within half a degree on average, with a spread of about four degrees either way (Ockendon and Gilbert, Journal of Knee Surgery, 2012). That study measured small bends in a clinic with a trained examiner, not this two-step reading at home, and nobody has measured the error of this page against a goniometer. So treat the number as yours to compare with your own earlier readings, taken the same way, in the same position. Your physical therapist measures with a goniometer; bring both numbers.

The milestones on your log use the ranges Rowe and colleagues measured in twenty people aged about 67 going about a day (Gait and Posture, 2000): walking and slopes use less than 90 degrees of knee bend, stairs and chairs 90 to 120, getting into a bath about 135, and they suggest 110 as a rehabilitation goal. Ockendon 2012 · Rowe 2000.

Educational information only, not medical advice. It does not replace your surgeon or physical therapist, and a number on its own is never a reason to push harder than your program says.