This question comes up from time to time as some commentators strive to “find the cause and fix the problem at all cost.” The argument is that if pain was gone, the person would simply return to their old life just as they were. And for what it’s worth, there’s certainly a relationship between pain intensity and disability, and pain intensity and distress – but it’s not simple.
One of the earliest papers I read when I was beginning my pain management career is one by Waddell, Main, Morris, Di Paola & Gray (1984). Gordon Waddell was an orthopaedic surgeon with an interest in low back pain – and an equal interest in what people do when they’re sore. In collaboration with Chris Main and others, he examined 200 people referred from family doctors for low back pain, and analysed psychological questionnaires administered to this same group. The process this team used to establish the results was rigorous by any standard, but especially rigorous at the time: they carried out pilot interviews and exams on 182 people, then carried out a further analysis of impairment and disability on a different group of 160 people, conducted this study with 200 people, and further cross-checked with a second group of 120 people.
What did the team find? Well, putting aside (for now*) the judgements about “inappropriate responses” to examinations and “magnified illness behaviour” they found that people who were highly distressed demonstrated more of these “inappropriate” and “magnified” behaviours. Makes sense to me as it did to Waddell and colleagues – their analysis was “They may develop as a largely unconscious and socially productive ‘cry for help’ but, unfortunately, in the absence of due help they may, in themselves, add to disability and become counterproductive.”** The table below (from p. 212 of this paper) shows that physical impairment was the most significant contributor to disability.
But hold on a minute! In the prestigious Volvo Award winning paper, Waddell (1987) then shows a wonderful graphic that encapsulates just how complicated this relationship is. In it, he shows that “objective physical impairment” (remember this is in back pain) has a correlation of just r=0.27 with pain, and r=0.54 with disability, while the relationship between pain and disability was only r=0.44.
In other words, if pain and disability were directly related, there would need to have a relationship of 1:1 between pain intensity and functional limitations. There is not – so “other things” intrude or influence the relationship between pain and disability. Again in this paper, Waddell shows that there is little difference in pain intensity between people who go and see a health professional for low back pain, and those who don’t (and seeking healthcare is a pain-related behaviour, or illness behaviour) – because what we do about pain depends a great deal on what we think is going on, and on what we think a health professional can do for us.
Now because these papers are old, they’ll likely be discounted so I dipped into the enormous literature on pain and disability. I thought I’d ask if having a successful surgery that removed pain led to a “return to normal.” A 2010 paper by Bade et al., found that in knee replacement surgery “Compared to healthy older adults, patients performed significantly worse at all times for all measures (P<.05), except for single-limb stance time at 6 months (P>.05). One month postoperatively, patients experienced significant losses from preoperative levels in all outcomes. Patients recovered to preoperative levels by 6 months postoperatively on all measures, except knee flexion range of motion, but still exhibited the same extent of limitation they did prior to surgery.” So that’s a study using boring old functional assessments and disability measures: what if the person was getting surgery so they could do something they enjoy, perhaps golf? Jackson et al., (2009) found that only 57% of golfers returned to golf after total knee arthroplasty, with 81% golfing as often, or more, than before their surgery – but only 14% walked the course after surgery. And these were keen golfers with no pain after their knee replacements!
Kovaks et al., (2004) also found that “Clinically relevant improvements in pain may lead to almost unnoticeable changes in disability and quality of life. Therefore, these variables should be assessed separately when evaluating the effect of any form of treatment for low back pain.” The two important tables showing how correlations changed over time are below. On day 1, a 10% increase in VAS (ie pain intensity) increases disability by only 3.3%, and quality of life by 2.65%. On day 15, a 10% increase in VAS increases disability by 4.99% and quality of life by 3.8%.
Now I’m not reporting a large number of studies because – well, there are a LOT of them. Suffice to say that while there is a relationship between pain intensity and disability, it is not straightforward, and simply reducing pain does not mean a person will return to what they love doing, even golf! I’ve chosen older studies because it’s kinda helpful to look at older research to show that these ideas are not new. This poor relationship between pain intensity and function is something we should know already. We should have been taught this in our training. So catch up with the literature please!!
The factors that influence disability are many, and they’re not just biological. They include fears (of reinjury, of pain flare-up), they include other peoples’ responses to them (advice from health professionals, workplace requirements, family responses). They are real and mean that even once there is an effective treatment for forms of persistent pain (and we’ll be waiting a while for these), rehabilitation from a whole person perspective is crucial. In fact, in the golfing study, all the physical measures (strength, ROM etc) were fine – so it’s not about physical fitness, nor about pain intensity, it is about people being people. So we also need to be people working with other people.
*We cannot detect malingering in people with pain because we have no objective measure of pain. Psychometric measures don’t measure malingering (see Tuck, N. L., Johnson, M. H., & Bean, D. J. (2019). You’d Better Believe It: The Conceptual and Practical Challenges of Assessing Malingering in Patients With Chronic Pain. Journal of Pain, 20(2), 133-145. https://doi.org/10.1016/j.jpain.2018.07.002), and neither can we.
**For what it’s worth, if anyone suggests the “Waddell signs” can demonstrate who is malingering – go read Waddell’s own words, where he states unequivocally that these are indications only of psychological distress.
Bade, M. J., Kohrt, W. M., & Stevens-Lapsley, J. E. (2010). Outcomes before and after total knee arthroplasty compared to healthy adults. Journal of Orthopaedic Sports Physical Therapy, 40(9), 559-567. https://doi.org/10.2519/jospt.2010.3317
Jackson, J. D., Smith, J., Shah, J. P., Wisniewski, S. J., & Dahm, D. L. (2009). Golf after total knee arthroplasty: do patients return to walking the course? American Journal of Sports Medicine, 37(11), 2201-2204. https://doi.org/10.1177/0363546509339009
Kovacs, F. M., Abraira, V., Zamora, J., Teresa Gil del Real, M., Llobera, J., Fernández, C., & Group, t. K.-A. P. (2004). Correlation Between Pain, Disability, and Quality of Life in Patients With Common Low Back Pain. Spine, 29(2), 206-210. https://doi.org/10.1097/01.Brs.0000107235.47465.08
Waddell, G., Main, C. J., Morris, E. W., Paola, M. D. I., & Gray, I. C. (1984). Chronic Low-Back Pain, Psychologic Distress, and Illness Behavior. Spine 9(2), 209-213.
Waddell, G. (1987). 1987 Volvo Award in Clinical Sciences: a new clinical model for the treatment of low-back pain. Spine, 12(7), 632-644.