⚠ DRAFT — readiness that feeds a CAPTE associate program; the PTA works under a PT
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K
Coach Katie
One of the most hands-on things a Physical Therapist Assistant does is measure how far a joint moves — its range of motion — and track whether it's improving. Let's learn what that means, meet the tool that measures it, and see real joint motions in 3D.
The basics
What is range of motion (ROM)?
Range of motion (ROM) is how far a joint moves through its normal arc. It's a core measure of rehab progress — a shoulder that could only lift partway last week and lifts higher this week is getting better, and ROM is how we put a number on it.
Active ROM (AROM)
The patient moves the joint themselves, using their own muscles. It tells you what they can do on their own.
Passive ROM (PROM)
You (or gravity/a device) move the joint for the relaxed patient. It shows the available motion without their muscle effort.
Quick rule of thumb: if the patient's muscles do the work, it's active; if you do the moving while they relax, it's passive.
The tool
The goniometer measures the angle
A goniometer is a protractor-like tool that reads the angle of a joint in degrees. Getting a reading you can trust is all about placement:
Fulcrum (axis)
The center of the goniometer sits over the joint's axis of motion — the point the joint rotates around.
Stationary arm
Lines up along the fixed bone (the segment that isn't moving), usually toward a bony landmark.
Moving arm
Follows the moving bone, tracking the limb as it travels through the motion.
Read in degrees
Where the arms cross on the scale is your joint angle. Same setup every time = comparable numbers.
Fulcrum on the axis, arms along the bones. If any of the three is off, the reading is off.
See it in 3D
Common shoulder motions
Every joint has named motions. On the shoulder, the ones you'll measure most often are flexion / extension,abduction / adduction, and internal / external rotation. Spin the model, then use the buttons to focus on each pair.
↕ Flexion / extension
Arm forward and up vs. back behind you.
↔ Abduction / adduction
Arm out to the side vs. back toward the body.
🔄 Internal / external rotation
Rotating the arm inward vs. outward.
Powered by the 360° Human Explorer. The 3D viewer is domain-locked and renders on theforce.health.
Why it matters
Consistency & comfort
Measure the same way every time. Same landmarks, same fulcrum, same starting position — that's what makes today's number comparable to last week's, so the PT can see whether the plan is working. A sloppy, eyeballed estimate can't show real progress.
Watch the patient, not just the dial. If a passive movement causes a wince or pain, ease off, note it, and communicate it to the supervising PT. Never force a joint past comfort to chase a number.
Know your role
The PTA's scope
A Physical Therapist Assistant works under the direction of a physical therapist. The PTA measures ROM and carries out the PT's plan of care — but the PTA does not evaluate, diagnose, or write the plan. When something changes (new pain, less motion, a red flag), you report it to the PT.
PTA (licensed role): requires a CAPTE-accredited associate degree and the NPTE-PTA exam. This module is readiness that feeds a college partner's program — not the program itself.
K
Coach Katie
Two moments from a rehab session. Pick the response that is caring, in-scope, and gets a measurement you can trust.
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Coach Katie
Five questions. 75% to pass, then make your pledge.
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Coach Katie
Learning sticks when you commit to a next step. Pick at least two pledges you'll actually do.
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