Barrett L. Dorko, P.T.

The term "flexibility" we commonly use in physical therapy means not only the quantity of movement available in a joint or group of joints but usually implies an easy excursion of periarticular structures in response to active or passive motion. In orthopaedics, establishing normal flexibility is commonly the goal of care when evaluation reveals a loss of normal, painless joint range and at least a theoretical connection between this loss and the patient's complaint.

Much has been made of the concepts of hypo and hypermobility;12 especially as related to spinal motion. More recently the additional problem of instability in selected spinal segments has been identified.34 This work has been useful in creating a framework for testing and treating patients according to a standardized series of provocative maneuvers designed to reveal dysfunction and lead the therapist logically toward a treatment regime.

Without implying that this approach is inappropriate or ineffective, I feel that another description of functioning in the patient is needed to explain the relationship between dysfunction and the experience of pain.

"Adaptive potential" is a term coined by Pettman and Fowler5 to refer to the ability of the shoulder girdle to withstand mechanical stress. I would expand and specifically define this term as "the ability of the system to tolerate a repetitive movement, a forceful blow or a prolonged position."

Such a definition embraces several qualities of normal functioning that flexibility alone cannot imply or necessarily ensure. The chart below lists the distinctions between flexibility and adaptive potential.

I have found this new terminology useful not only in assessment but in more accurately explaining clinical phenomena as treatment progresses.

Adaptive potential exists as a category of function that is primarily biomechanical in nature. I feel I should emphasize, however, my own bias toward adverse mechanical tension in the nervous tissue being the primary cause of nociceptive firing.6 Of course, without mechanical deformation of these nerves (in the absence of chemical irritation) no pain would be experienced.7 Loss of normal, painless excursion of the nerve trunks or roots could certainly be accounted for by an acquired twisting within the connective tissue, chronic expansion of the contractile tissue (guarding) or bony migration. Sunderland8 reminds us that the slackness of the nerve trunks and the mobility of the nerve root in the foramen is part of the protective mechanism against nervous irritation. The loss of this movement is a biomechanical problem leading directly to pain that may not include the loss of joint range. Since the difference anatomically between the central and peripheral nervous system is primarily topological, this increased tension throughout the nervous tissue may know no boundary, creating symptoms that extend everywhere and are rapidly altered with a variety of unique positions. I see this quite often.

Measuring the patient's flexibility in such a situation might prove to be confusing and inappropriate for a number of reasons. They might display excellent range but report on history that attaining the position requested is easy; it's maintaining it painlessly that is impossible. The motion itself and its maintenance is easy but, historically, repeated movement is painful (no pathology is evident). Flexibility is full, but even a slight jarring of the system produces prolonged and/or widespread pain. Most therapists will recognize some of their patients in these descriptions.

If we can accept the loss of adaptive potential within the nervous and/or associated connective tissues as the underlying biomechanical explanation for symptomatology, assessment and treatment might be dramatically altered. For example, specific segmental mobility of the spine becomes less important than the historical details of tolerance for movement or position. Treatment would be more likely to emphasize coordination of painless motion rather than active stretching to enhance joint range.

In light of this concept, the mechanical production of pain would require an adequate correlation of two processes; the amount of mechanical deformation present and the adaptive potential available. Both of these may vary wildly as we move and learn and respond to our environment.

Perhaps we can say that hypomobility leads to pain because it reduces the system's adaptive potential, producing pain with normal motion that would ordinarily be accounted for comfortably. It is equally logical to say that hypermobile joints allow motion to occur beyond our naturally occurring adaptive abilities.

Including the concept of adaptive potential does not essentially change every treatment approach, but it clarifies our patient's predicament and may lead us toward care that varies appropriately with the changing nature of their system.


Demonstrated by measurable joint range.

Adaptive Potential

Demonstrated by a painless response to repetitive movement, a forceful blow or a prolonged position.

Implies easy, painless active or passive excursion of tissue in many planes. Implies the ability to account for, tolerate and disperse long or short-term force.
Primarily dependent on connective tissue length and secondarily on CNS activity. Primarily dependent on CNS "plasticity" and secondarily on connective tissue length.
Can be seen and measured with relative ease Difficult to measure; typically inferred by history.
Tends to change slowly in either direction May rapidly alter in response to a series of processes

1. The Spinal Lesion by Paris, Pegasus Press

2. Manual Therapy for the Extremity Joints by Freddy Kaltenborn

3. "Pathology and pathogensis of lumbar spondylosis and stenosis," by Kirkaldy-Willis, W.H. Wedge et al. Spine 3:319

4. "The examination and treatment of segmental hypermobility" by Jim Meadows, P.T. presented at the 1988 National APTA/CPA convention

5. "The Functional Shoulder Girdle" by Pettman and Fowler, Proceedings of the Fifth International Conference, I.F.O.M.T.

6. "Adverse Mechanical Tension in the Central Nervous System" by Barrett Dorko, P.T. Forum Vol 4 No. 43

7. The Lumbar Spine and Back Pain edited by Malcolm Jayson, Grave and Stratton

8. "Traumatized Nerves, Roots and Ganglia" by Sunderland in The Neurobiologic Mechanisms in Manipulative Therapy, Plenum Press