Range of movement (ROM) is specific to each joint in the body and describes the degrees of motion a joint can move in a certain direction. Joints have different degrees of freedom depending on their shape and function. The knee allows movement in one plane, the bending and straightening you need to kick a ball, while the hip allows movement in three planes, enabling a contortionist to get her leg behind her head. These different directions all have normative values, luckily not based on the contortionist.
Range of movement is assessed with a goniometer, an odd looking protractor. Range of movement is affected with injury. The injury doesn’t have to be of the joint itself to affect its mobility, a lower back disc bulge will affect the hip’s flexion range of movement because of irritation to the sciatic nerve and Achilles tendonitis will affect the ankles dorsiflexion ROM, etc.
