Definitions for "RANGE OF MOTION"
The degree of motion in a joint. Passive range of motion (P.R.O.M.) is the degree of motion in a joint when the joint is moved by some other person. Active range of motion (A.R.O.M.) is the degree of motion accomplished by the efforts of a person in moving his or her own limb.
(ROM) refers to the flexibility of joins such as elbows, wrists, ankles, knees, hips. Spastic muscles make joints stiff; this decreases the range of motion (span of movement possible) of the joint.
The range through which a joint can be moved, usually flexion and extension. Due to an injury, the knee may, for example, lack 10 degrees of full extension.  It can also refer to movement of joints by a therapist or nurse through their range of motion to preserve function for those on prolonged bedrest.