Range of motion (ROM) is the arc of motion that occurs at a joint or series of joints in the body in a specific plane of motion. ROM involves a joint or body segment moving from its neutral position to its full potential. The neutral position is referenced from the body's anatomical neutral position, and the full potential motion of a joint is referred to as the end ROM.
Active range of motion, also abbreviated AROM, is defined as the arc of motion achieved through voluntary movement produced by an individual. AROM is produced by contractions of specific muscles that cross the joint, causing an angular motion to occur. Successful performance of full AROM depends on multiple factors. These include, but are not limited to, the following: an intact and normal function of the neuromuscular unit, intact muscle and tendon transcending the joint, normal strength, normal joint congruency and anatomy, and absence of soft tissue restriction.
Passive range of motion, commonly referred to as PROM, is defined as the arc of motion achieved through the assistance of external forces, without active assistance from the individual. PROM occurs only with complete lack of voluntary assistance from any muscle that crosses the joint. An individual receiving PROM would completely relax and play no active role in producing the movement. The achievement of full PROM depends on normal joint congruency and anatomy, and normal extensibility of the joint's surrounding soft tissue structures.
A joint or body segment moves through an ROM in any 1 or more of the 3 cardinal planes of motion in space: (1) sagittal, (2) frontal, and (3) transverse. Every joint in the body has a specific ROM in each plane of motion depending on the joint's structure. Understanding the ROM available at a given joint depends on understanding both the osteokinematic and the arthrokinematic movements occurring at the joint.
Osteokinematics is the study of the movement of bones relative to the 3 cardinal planes of motion of the body. The osteokinematic movement of a joint is measured and recorded as a joint's ROM. This can be measured as AROM or PROM depending on the methodology used. Each plane of motion, or independent movement allowed at a joint, is referred to as a joint's degree of freedom. Thus, a joint can have up to 3 degrees of freedom, depending on the joint's structure. When a health care clinician measures the ROM, that person is measuring the osteokinematic motion at a specific joint and in a specific plane of motion.
Arthrokinematics is the study of the motion occurring between the articular surfaces of a joint. Joint ROM depends on the normal arthrokinematic function in the joint being measured. Arthrokinematic motion is determined indirectly through observation of a joint's movement, with knowledge of the shapes of the articulating surfaces. Most joint surfaces are curved, with one end of a joint taking on a concave shape and the other taking on a convex shape. These shapes of articulating surfaces of a joint serve to improve joint congruency, increase surface area to dissipate contact forces, and guide osteokinematic movement.
The fundamental arthrokinematic motions that occur between joint surfaces during osteokinematic motion are roll, slide, and spin. The direction in which these arthrokinematic motions occur depends on whether the motion is occurring due to a concave-on-convex motion or a convex-on-concave motion. These factors can inhibit the available ROM at a joint, and it is the role of the health care professional to determine if faulty arthrokinematics are causing dysfunction in the ROM.
ROM is routinely assessed by health care professionals, especially physical and occupational therapists. Physical and occupational therapists evaluate ROM to link specific deficits to limitations in daily activities. Through comprehensive knowledge of the functional anatomy of all joints in the body, ROM can be assessed and measured. When deficits are present, the assessment of ROM not only provides useful information in understanding the functional limitations that can occur but also gives insight into the treatment for those deficits to improve function.
ROM is typically measured with goniometry. Goniometry is derived from the Greek gonia meaning “angle” and metro meaning “measure.” Goniometry is therefore defined as the measurement of angles. To examine ROM with a goniometer, the examiner aligns the measuring instrument's arms along the proximal and distal bones of the joint, with the axis of rotation of the goniometer centered through the middle of the joint. As previously described, the starting point for measure is the anatomical neutral position of the joint. The end point of the ROM is taken when the distal segment of the joint can no longer move in the plane of motion being measured without restriction or risk of injury.
Alternative measures for joint ROM include the use of an inclinometer or a measuring tape. An inclinometer is an instrument that measures the inclination of an object with respect to gravity. Measurement using this instrument involves the alignment of the joint being measured in a gravity-dependent position. Tape measures are used occasionally and often involve the use of measuring distances between a stationary landmark, either anatomical or external, and a reference point on the extremity or joint being tested.
Assessing and measuring both AROM and PROM provide the physical or occupational therapist or qualified health care professional with a significant amount of information about a patient. Both AROM and PROM depend on normal joint integrity and congruence, and normal elasticity of all soft tissues surrounding the joint. However, when assessing AROM and PROM, there are definitive differences. AROM depends on voluntary muscle contraction and thus could be limited by a patient's willingness to move, muscle strength, neuromuscular function, coordination, and arousal. AROM also tells a therapist or a qualified health care professional about a patient's functional capability or movements that cause pain.
PROM is assessed to provide the amount of movement possible at a given joint. PROM is slightly greater than AROM because every joint has a slight amount of motion that is not under voluntary control. The additional ROM available is due to the stretch of the tissues surrounding the joint and the reduced bulk of relaxed muscles. PROM is assessed by a therapist or a qualified health care professional to assess the integrity of the joint's structure and the extensibility of the joint's capsule, ligaments, and other soft tissue restraints.
In the assessment of PROM, normal anatomical structures limit the end ROM, presenting an apparent barrier to further ROM. This barrier or end of PROM is referred to as the end feel of an ROM. Physical and occupational therapists as well as other trained health care professionals routinely assess the end feel of a joint ROM to determine if structural deficits are present. Normal end feels range from soft to firm to hard. “Soft” implies soft tissue approximation; “firm” end feels can be caused from muscular, capsular, or ligamentous stretch; and “hard” end feels are usually bone contacting bone. Abnormal end feels occur when limitations of ROM occur sooner or later than usual and imply many different pathologies depending on their specific findings to the trained examiner.
When PROM exceeds the normal ROM for the given joint in the given plane of motion, it is deemed hypermobile. If the ROM is less than the normal or expected, it is considered hypomobile.
When assessing ROM, it is recommended to test both AROM and PROM. PROM relays information on the total capacity of a joint to produce an ROM as per the joint structure and end feel, and AROM provides information on the individual's ability to produce motion at a joint.
Besides the aforementioned differences and limitations in AROM and PROM, there are multiple other factors that affect the ROM available at a given joint. These include, but are not limited to, the following: age, gender, BMI, occupational or recreational activities, and joints involved with 2-joint or multijoint muscles.
Numerous studies have shown the effects of aging on ROM. In general, most joints in the extremities and axial skeleton, though sometimes motion specific, decrease in their ROM with aging. Most studies regarding gender and aging are also joint specific and motion specific. With regard to occupational and recreational activities, individuals often create hypermobility or excess ROM through recurrent postures of the axial skeleton or motions in an extremity.
A multijoint muscle sometimes limits the amount of PROM available at all the joints in which it crosses. When the muscle is elongated over one joint, it creates a passive tension over the second joint, limiting the amount of PROM at that joint. This limitation is termed passive insufficiency. Clinically, this condition is often observed at the hamstrings muscle group, rectus femoris, triceps brachii, and extensor digitorum.
Therapeutic techniques are often implemented to either restore full ROM in a joint that has limited ROM or decrease ROM in a hypermobile joint. Methods will vary according to the status of the patient or an individual with abnormal ROM. The patient is assessed to determine whether the limitation is due to passive restriction from the joint capsule, for example, or due to decreased muscle strength. Patients should be thoroughly assessed, and the techniques for treating the limitations should be specific to the individual.
Some contraindications to performing ROM techniques are as follows: suspicion of dislocation or fracture, motion that will inhibit healing process or cause further injury, presence of any pathology that may worsen or become unstable with ROM exercise. Caution should be taken in measuring ROM in individuals who are in acute pain, are under the influence of pain medications or muscle relaxants, have just had an acute injury, or have hypermobility.
Methods to improve limited ROM are conducted by physical and occupational therapists or other qualified health care professionals. Techniques in an individual with passive limitation involve passive stretching of soft tissues to include muscular stretching to reduce muscular tension, and joint mobilizations to improve elasticity of joint capsule or restore proper arthrokinematic motion in the joint. If the patient is limited in active motion, the techniques should focus on muscular strength, activation, or coordinated movement. This individual may benefit from isolated muscle strengthening, neuromuscular facilitation techniques such as proprioceptive neuromuscular facilitation, or biofeedback techniques with the goal of improving voluntary muscle control through a greater ROM.
Methods to improve a hypermobile joint or one with excessive ROM could also be conducted by a therapist or qualified health care professional. These techniques involve protection of joint integrity by avoiding stretching or positions beyond the normal ROM. The focus for interventions with this individual is to improve neuromuscular control of the joint to improve joint stability. This is achieved through training of muscular co-contraction at the involved joint, rhythmic stabilization, and proprioceptive neuromuscular facilitation techniques to improve dynamic and static joint stability.
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