Range of Motion (ROM) describes the extent to which a joint can move through its typical arc of movement. This measurement is a fundamental component of musculoskeletal health, indicating the flexibility and mobility of a joint and the surrounding soft tissues. When movement is compromised due to injury, illness, or weakness, specific techniques are employed to maintain or restore this capacity. This article focuses on Passive Range of Motion, a technique where movement is accomplished entirely by an external source.
Defining Passive Range of Motion
Passive Range of Motion (PROM) is the movement of a joint through its available range without any muscular effort or contraction from the individual. The movement of the limb or body part is fully dependent on an outside force. This external force can be a trained healthcare professional, a caregiver, or a specialized mechanical device, such as a Continuous Passive Motion (CPM) machine.
The defining characteristic is the complete relaxation of the muscles that normally control the joint, allowing the external force to gently move the joint through its arc. This technique is necessary when a person is paralyzed, unconscious, temporarily too weak to move, or when muscle contraction is medically contraindicated following certain surgeries. Because the patient is not generating the force, the joint is typically moved to the point where the therapist feels the natural tissue resistance, or “end-feel,” of the joint.
Therapeutic Goals of Passive Movement
The primary purpose of performing PROM is to preserve the physical integrity of the joint and its surrounding soft tissues when active movement is impossible or unsafe. Moving the joint through its available arc helps maintain the existing flexibility and mobility of the joint capsule and ligaments. This consistent, controlled movement helps prevent joint stiffness and the development of contractures, which are severe shortenings of muscles and connective tissues.
Passive movement promotes joint health by stimulating the production and circulation of synovial fluid within the joint space. This fluid provides lubrication and delivers nutrients to the avascular articular cartilage, which is essential for preserving the health of the joint surfaces. Passive movement also assists in promoting localized blood flow and venous return, which helps manage swelling and supports the healing process, especially in the early stages following an injury or surgery. PROM also serves as an assessment tool, allowing the clinician to evaluate the joint’s status and identify any restrictions or pain points before the patient can actively participate in rehabilitation.
Comparing Passive, Active, and Active-Assistive Range of Motion
The three main categories of joint movement are distinguished by the source of the moving force and the level of the patient’s muscular involvement. Passive Range of Motion (PROM), as defined, involves zero muscular effort from the patient; the movement is entirely external. In contrast, Active Range of Motion (AROM) is executed solely by the patient’s own muscles contracting and moving the joint through its full available range. AROM requires neuromuscular function and is used to maintain or increase muscle strength and coordination.
The third category, Active-Assistive Range of Motion (AAROM), represents a hybrid approach. The individual initiates the movement by contracting their own muscles, but an external force is required to complete the movement through the full arc due to weakness or pain. For example, a patient may lift their arm halfway, and a therapist or a specialized pulley system provides the necessary assistance to move it the rest of the way overhead.
The choice among these three types of movement depends on the patient’s condition and the stage of healing. PROM is indicated when muscle contraction is undesirable, such as immediately after a severe injury or surgery, to protect healing tissue. AAROM is employed as a transitional step when the patient has regained some muscle function but is not yet strong enough to move the joint independently against gravity. Finally, AROM is used when the patient can safely and independently move the joint, with the goal of improving functional mobility, strength, and endurance.