Range of Motion
ROM. The extent of movement possible in a joint, measured in degrees. Active, passive, and active-assisted motion in recovery.
What range of motion is
Range of motion (ROM) is how far a joint can move in a particular direction. It’s measured in degrees using a handheld tool called a goniometer. A normal knee, for example, can bend from 0° (fully straight) to about 140° (fully bent). A normal shoulder can rotate through more than 180° in multiple directions. After injury or surgery, ROM is often reduced due to pain, swelling, stiffness, or muscle guarding. Restoring ROM is a key goal of post-operative rehabilitation.
Active ROM (A-ROM)
Active range of motion is movement you generate yourself using your own muscles. You bend the knee or rotate the shoulder without anyone helping. A-ROM reflects both the mechanical limits of the joint and your willingness to use your muscles despite pain. After surgery, A-ROM is often reduced initially because pain and swelling discourage movement. As pain settles and strength returns, A-ROM improves.
Passive ROM (P-ROM)
Passive range of motion is movement imparted by someone else (a therapist or doctor) or by a machine (a CPM device, or continuous passive motion machine) while you relax and let the joint move. P-ROM helps maintain the joint’s mechanical mobility and can reduce stiffness. After some surgeries, P-ROM may be greater than A-ROM initially because a therapist can move the joint without the patient guarding against pain. P-ROM is often used immediately after knee replacements and some shoulder surgeries.
Active-Assisted ROM (AAROM)
Active-assisted range of motion is a hybrid: you move the joint using your own muscles, and a therapist provides gentle help to take you a bit further. AAROM is often used early in recovery when you have some strength but pain or weakness limits your ability to move fully. The therapist’s assistance encourages deeper motion while allowing you to control the effort.
Why ROM matters in recovery
Regaining ROM is critical. Stiffness can persist long after surgery if ROM isn’t aggressively restored early. After a knee replacement, for example, even a 10–degree loss of full extension (straightness) can cause a permanent limp. After a shoulder repair, loss of external rotation can limit overhead activities forever. Physical therapists focus intensely on ROM in the first 6–12 weeks because that window is crucial for preventing permanent stiffness.
Normal ROM for common joints
- Knee: 0° (full extension) to 140–150° (full flexion). Some hyperextension is normal.
- Hip: 0–10° extension, 110–120° flexion, 40–45° abduction (away from center), 20–30° adduction (toward center), 40–45° internal rotation, 45–50° external rotation.
- Shoulder: 180° flexion (forward), 50° extension (back), 170–180° abduction (out to side), 70–80° internal rotation, 80–90° external rotation.
- Ankle: 20° plantarflexion (toe-down), 10° dorsiflexion (toe-up), 30° inversion (sole inward), 20° eversion (sole outward).