A recent study appearing in the Journal Manipulative and Physiological Therapeutics has examined the evidence for a correlation between lumbar proprioception and clinical low back pain. It was a systematic review that searched 6 major databases and returned 5 studies (with a total of 204 patients) eligible for inclusion. At the end of the process, researchers have been able to claim that there is a relationship between pain intensity and proprioception, albeit a complex one.
The nature of pain perception is complex and subjective. Research has revealed sex, age and ethnicity all impact on pain perception . Other factors that feed into the pain experience include “genetic, developmental, familial, psychological, social and cultural variables” . All considered, the reality is that two people could suffer from the same condition to the same severity, and yet have vastly different experiences of pain and pain-related disability.
While altering any of these variables may be outside the purview of the chiropractor, there is one thing we have been found to impact: proprioception .
That’s what makes this latest systemic review so interesting. Researchers, Ghamkhar and Kahlaee, scoured 6 leading medical databases for papers that recruited patients with chronic non-specific low back pain longer than 3 months in duration, and that assessed proprioception and pain intensity or pain-related disability . A series of exclusion criteria were set up to ensure the validity of the review.
All relevant studies defined non-specific low back pain as “lumbar pain without a specific established anatomical or neurological cause” and the sample sizes in each eligible study ranged from 15-90 participants. One study looked at women only, but the other 4 studies included both sexes, and pain intensity ranged from 3.3-6.3 on a 0-10 scale.
Proprioception was measured via joint repositioning errors (JRE) in 4 of the studies, and “threshold to detection of passive motion (TTDPM)” tests in 1 study. The researchers explained :
The JRE test measures how accurately a participant can actively or passively reproduce a “target position.” Three common JRE parameters are (1) absolute error (AE), which is the unsigned difference between the target and the reproduced position, indicative of repositioning accuracy; (2) constant error, defined as repositioning bias, which shows the overshoot or undershoot repositioning error; and (3) variable error, indicating variability error and calculated from constant error scores.”
The TTDPM test measures sensitivity to detection of passive lumbar spine movement at a constant velocity and indicates the earliest point the participant senses any positional change.”
Interestingly, the findings revealed that, (in CNSLBP sufferers) “pain-related disability was significantly positively correlated with flexion and extension AE [absolute error].”
Furthermore, they found that there was “no correlation between pain intensity and AE in any movement directions.” In other words, impaired proprioception (regardless of the direction of movement) was to positively correlated.
The researchers remarked : “Although the limited evidence agrees on a fair to moderate correlation between proprioception impairment and pain-related disability, there is no consensus on such a relationship between proprioception and pain.” This makes the systemic review, and further research into the matter, an important undertaking so that the limitations of such studies can be accounted for.
What we do know from this study is that proprioception impairment may be a mechanism for pain perception. Whether that is because of decreased sensory feedback, postural and muscle control, predisposition towards injury and micro-trauma or other psychological factors remains to be seen. Again, researchers remarked that “the pain interference model suggests that, in the presence of pain or fear of pain, the CNS [central nervous system] chooses to suppress the motor activity in the pain-related region as a protective mechanism…However, in most of the recent studies, impaired proprioception could not be explained by pain.”
At this point in time, there is a paucity of chiropractic-specific research into the correlation between proprioceptive impairment and pain perception. However, we do have a growing evidence bank that points to a link between chiropractic care and improved proprioception, as well as research on how the adjustment may alter the way the brain processes pain [3, 5]. Thus we have indicators that, for low back pain and other issues, chiropractic may be a more valuable piece of the pain and function puzzle than many currently think we are.