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Understanding Passive Range of Motion

Despite the increased use of high-tech diagnostic procedures, assessing the function of soft tissues involved in locomotion is still best done through physical examination. We derive some of the most valuable assessment information from relatively straightforward procedures like active and passive range of motion tests. While you may have learned the basics of performing active and passive range of motion tests, you might not have fully explored how to use this information effectively in a clinical environment. This article focuses on passive range of motion (PROM) evaluations and the valuable information you can derive from these procedures.

PROM evaluations help identify various kinds of problems in the soft tissues. It is best to perform PROM after evaluating active movements. This order is primarily for the efficiency of the evaluation. If there is no pain with active movement in the motion you are testing, it is unlikely that there would be pain with passive motion. Therefore, performing specific passive movements may not be necessary. Also, when you evaluate active movements first you can see the client’s self-imposed limitation on movement.

To perform a passive movement evaluation, have the client relax as much as possible preceding the movement. You want to have the greatest degree of muscular relaxation before beginning the movement. That will improve the accuracy of the evaluation as less muscular effort is involved.

One of the most important factors to investigate with passive range of motion testing is the end-feel. The end feel is the quality of movement that is perceived by the practitioner at the very end of the available range of motion. The end-feel can tell a great deal about the nature of various pathologies. There are often different categories of end feel. These are six different commonly used end feel descriptions.

Bone to bone- this is the sensation where motion is stopped by two bones contacting each other. An example is the end-feel for extension of the elbow.

Muscle spasm- when muscles are in spasm, they may abruptly halt motion before what should be the normal range of motion. The client may feel pain near the end range of movement due to stretching of the spasming muscle.

Capsular or Tissue Stretch- this end-feel describes motion limited at the end range by the joint capsule or other soft tissue becoming taut. This end feel is frequently described as a “leathery.” A capsular end feel is evident at the end range of external rotation of the shoulder in a normal shoulder. This end feel is also called the tissue stretch end feel to extend it to other tissues, such as muscles, that stretch at the end range of motion. An example of the tissue stretch with muscles would be hip flexion with the knee held in extension where the hamstrings limit the movement.

Springy block- this end feel is the sensation of motion stopping short of where it should be, accompanied by a rubbery or springy feeling at the end. It occurs most often in joints where a piece of loose cartilage (like the meniscus in the knee) may be blocking full motion.

Tissue approximation- this is the end-feel where motion stops by two masses of soft tissue pressing on each other. An example is in flexion of the elbow.

Empty- this end-feel is one where there is not a mechanical limitation to the end of the range, but the client will not let you go any farther because the pain is too much.

Passive motion evaluations are essential to help identity which tissues might be the primary source of pain for the client. The locomotor soft tissues of the body can be divided into two categories: contractile and inert. Contractile tissues are those that transmit force in the contraction process (muscle and tendon). Inert tissues are all the others that may get moved during the process of joint motion but do not actively produce contraction forces. Passive motion testing focuses mostly on inert tissues since there is no muscular action. However, if a muscle is hypertonic, it may be painful when stretched in the direction opposite that of its action. For example, lateral rotators of the shoulder that are hypertonic may be the source of pain at the end of a passive medial rotation movement because they are stretching.

Passive motion evaluation is described in great detail in the osteopathic literature with the concept of motion barriers. Motion barriers are a means of clarifying where there is a pathological limitation to movement. Figure 1 shows a schematic representation of motion barriers.

Figure 1: Motion barriers

In Figure1 Nrepresents the normal mid-range of movement for a particular joint segment. There is an equally available range of motion on each side of that point. Ph represents the physiological barrier to motion. The physiological barrier is the point where resistance to motion is first felt. The physiological barrier is generally the end range of movement available with active movement. Note that there is an elastic nature to the physiological barrier because you will feel resistance to motion begin, but you can still achieve more motion in that direction to a certain degree.

The anatomical barrier is represented in this diagram by A. It is the end of available motion that you can’t pass without causing tissue damage. For example, in performing a lateral rotation of the shoulder, the client can get to a specific end range of motion that will usually indicate the physiological barrier. However, during passive stretching, the clinician can increase the degree of motion in the shoulder a little more to the anatomical barrier.

The barrier concepts are most valuable for looking at various soft tissue pathologies that limit motion. For example, in Figure 1, a pathological barrier is represented. For some reason, the person can’t move beyond this point. Therefore when performing a passive range of motion evaluation, the clinician will encounter the pathological barrier before either the physiological or anatomical barrier. Depending on the cause of the pathological barrier, soft tissue treatment aims at moving the pathological barrier in the direction of the physiological and anatomical barriers until the client has full and normal motion restored.

Concepts used in passive range of motion evaluation such as end-feel and motion barriers are beneficial for evaluating the nature of various problems. Knowing which tissues are most likely the cause of various issues aids us in choosing the most appropriate treatment methods.

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