The Integrated Components of Stability

Use of the term stability is widespread across the physical and rehabilitative medicine disciplines. Stability is generally referenced as a positive outcome we are looking to achieve in order to help alleviate our patient's presenting complaint. Stability is often referenced as the missing ingredient in our patient's condition and therefore is frequently thought of as something we must establish in order to restore function.

However, stability and function are two separate and distinct entities, so determining where stability training and development fits within a treatment and rehabilitative plan of management can be flawed if the practitioner treats stability and function as interchangeable entities. You can be stable, but not functional. Severe degenerative changes on the lumbar spine is an example of stability without an optimum level of function. Another example involves the spinal adaptations seen in response to lower back pain, when there is an increase in stiffness and stability of the spine, which can be protective initially, but detrimental to long-term recovery and restoration of function. (You can also be functional, but not stable. A circus contortionist is a good example.)

Stability: Parts of the Whole

I believe stability is as much centered on its parts as it is about the whole. Clinically, when we look at neuromusculoskeletal stability, we should break it down into the segments that together, form the observed outcome we are typically describing when referencing stability.

Panjabi's initial description of segmental stability, involving passive, active and neural components, is a great building block to segmenting stability into more identifiable components. I believe each of the components forms its own stability models, which when it comes to human function, become interdependent on each other to achieve optimal function. In order to help organize both the diagnostic and interventional breakdown of stability, I use the following three categories; arthrokinematic stability, myokinematic stability and neurokinematic stability.

Arthrokinematic stability pertains to how well the joint or joints involved are able to maintain centration throughout the movement objective. Arthrokinematic instability involves a non-overt pathological inability to maintain centration of a joint. A loss of centration disrupts the ability for the entire system to function with efficient control.

Myokinematic stability involves the myofascial structures and their structural integrity. If there has been excessive fibrosis due to previous injury or tendinopathies affecting load transfer capabilities, then once again, efficient movement patterns become altered. Myokinematic stability also includes the bioenergetics and perfusion needed to perform the intended tasks. If perfusion is compromised due to previous trauma or deconditioning, or if there is inadequate nutrient flow to working muscles, the "stability" of the system will become compromised.

The third component of neuromusculoskeletal stability is neurokinematic stability, relating to the operating system behind human movement and function. Neurokinematic stability involves the timing and coordination of muscular activation. This form of stability provides the sequencing of motor-unit recruitment to allow for smooth, efficient motions in order to facilitate effective transfer of forces that the body must generate and absorb. Neurokinematic stability is compromised following an injury and can often become the source of chronic pain and dysfunction.

When Stability Breaks Down: A Clinical Scenario

To look at the breakdown of stability in the clinical sense, let's take a look at the clinical presentation of chronic sacroiliac dysfunction. Sacroiliac stability is accomplished by a combination of form closure and force closure. Form closure would constitute arthrokinematic stability. If the patient had presented with a history of discomfort after falling on their backside, it would be plausible to think that there may be an impact associated loss of arthrokinematic stability. In this case, if your evaluation determines an alteration in joint centration, articular adjustments would be implemented as a primary intervention.

Force closure, on the other hand, is accomplished through the combined co-activation of a group of muscles including the biceps femoris, gluteus maximus, lumbar paraspinals, lumbar multifidi and the thoracolumbar fascia. Both the myokinematic and neurokinematic categories of stability would govern force closure around the sacroiliac joint.

If the patient presented with a history of inactivity and lack of tone in the gluteus maximus due to deconditioning and sitting all day while at work, the muscles would lack the appropriate means to provide the support necessary to properly "stabilize" the SIJ. In this case, exercise conditioning and work modification strategies would be employed as the primary intervention in order to help improve the tone and physical capacity of the deficient musculature.

The patient may also have presented with a history of lower back pain prior to the onset of the chronic SIJ problem. Nociceptive input to the central nervous system alters the normal motor commands to both the injured muscles, signaling the nociceptive signals, as well as all of the synergistic supporting muscles. This alteration in motor output leads to deficits in neuromuscular control. Neuromuscular control is a primary ingredient in maintaining optimal neuromusculoskeletal stabilization.

Research has also shown a loss in cross-sectional area within a damaged muscle, as well as infiltration of fatty tissue, even after the symptoms associated with the initial trauma have subsided. In our case of chronic SIJ pain, if the patient presented with a history of lower back pain, there may have been a loss of function along with fatty infiltration of the multifidi, which could have led to the onset of SIJ aggravation.

For this presentation, strategies focused on reinstating neuromuscular control and activation of the supporting musculature are of primary importance. Therapeutic strategies to help modulate nociceptive drive to the central nervous system have immense clinical value, not only in reducing the clinical presentation of pain the patient is experiencing, but also for helping to normalize motor tone and activation necessary for optimal neuromusculoskeletal stability.

Physical Exam Applications

Segmenting neuromusculoskeletal stability into its components also helps to structure your physical exam. Neuromusculoskeletal stability is dynamic in nature; therefore, the physical exam should be dynamic. This point highlights the need to take your evaluations off the table and implement dynamic movement evaluation strategies. There are a number of new resources available to clinicians in order to help develop such skills. It provides a structured approach to evaluating movement and the components involved with neuromusculoskeletal stability.

As many of the components of neuromusculoskeletal stability are functional in nature, such as neurokinematic stability, it can be difficult to evaluate "stability" during a clinical exam. With body movements, the ability to compensate and still achieve the movement objective can further complicate the ability to isolate the source of the presenting complaint. Compensatory mechanisms are the body's attempt to counterbalance any deficits in structure or function and can often be difficult to identify unless proper training is undertaken to develop such skills.

As a clinical example, if we look at a presentation of rotator-cuff impingement of nontraumatic onset, the impingement is often due to mechanical aggravation as a consequence of functional degradation. Being able to identify the functional deficits in stability, whether it is arthrokinematic, myokinematic or neurokinematic, can even assist in helping to prevent such conditions from occurring in the first place.

Movement evaluations can help identify faulty patterns of control that, if left unrecognized, can lead to an increase in mechanical stress and strain on myofascial and articular structures. Examples of such forms of dynamic evaluations include a squat test - a global test of neuromusculoskeletal capacity, primarily looking at lumbopelvic and lower extremity function; or an anterior glide test on the glenohumeral joint, serving as a local evaluation of arthrokinematic stability.

I cannot overstate the clinical importance of segmenting neuromusculoskeletal stability into its integrative components in order to help isolate the primary deficit associated with the presenting complaint. Once we have segmented stability into its three components, keeping in mind that the whole system and all of the components are interrelated in achieving optimal neuromusculoskeletal function, we must then implement dynamic movement evaluation strategies to help identify deficits in control and stability.

This form of clinical approach will allow chiropractors to further enhance their skills as musculoskeletal diagnosis and treatment experts, because of course, the most important issue in treating any presenting complaint is recognition of the source of the complaint versus the symptoms.

Resources

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