Weight loss from bariatric surgery alleviates many illnesses, and has resulted in many medical improvements for those undergoing what should not simply be considered a cosmetic procedure. Some are fortunate enough to be able to lower the dose or even eliminate medications for conditions such as diabetes and high blood pressure.
It has also been found that knee pain improves, and apparently not simply because there is less force on a given knee. In general, obese individuals have more musculoskeletal pain than those who are not obese, and not just involving the weight-bearing joints. While obese patients may experience more pain due to excess loading across weight-bearing joints, it could also be that adipose tissue-related generation of biochemicals are causing low-grade inflammation within joints—and contributing to pain.
Both persistent inflammation and/or mechanical tissue injury can lead to alterations in nervous system nociceptive processing in animal models. One such alteration is an increased responsiveness of the peripheral and central nervous systems to nociceptive input (i.e., peripheral and central sensitization). Peripheral and/or central sensitization can result in heightened pain severity, as has been observed in persons with knee osteoarthritis, low back pain and other chronic musculoskeletal disorders.
Peripheral and/or central sensitization can result in chronic pain.
A recently published study had the goal to evaluate changes in pain (at the knee and elsewhere) and pain sensitization in obese persons with knee pain undergoing bariatric surgery compared with similarly obese persons undergoing medical management.
Indeed, in this study, pain scores improved in those undergoing bariatric surgery, whereas no significant improvements were seen in a comparable medically managed group. In the presence of sensitization, nociceptors respond to stimuli that they would normally not respond to. However, due to neuroplasticity, removal of the stimuli that contribute to sensitization may normalize nociceptor functioning.
Thus, with substantial weight loss, a decrease in obesity-related inflammation and/or mechanical loading may be sufficient to lead to improvements in sensitization.
Of course, there may be other explanations for improved sensitization after bariatric surgery that were not assessed in this study, including, for example, improved sleep quality, mood, and physical activity.
And it remains to be seen how much weight needs to be lost before there is a significant reduction in pain.
Better yet, exercise and eat well—and don’t be a candidate for bariatric surgery in the first place.
Stefanik, J. J., Felson, D. T., Apovian, C. M., Niu, J., Clancy, M. M., LaValley, M. P. and Neogi, T. (), Changes in Pain Sensitization after Bariatric Surgery. Arthritis Care Res. Accepted Author Manuscript. doi:10.1002/acr.23513