Several recent observations caused me to wonder about the impact of RA on muscles. In the almost five years since being diagnosed with RA, I’ve seen a steady decrease of muscle strength coupled with an increase in periodic pain and aching in muscle tissue. I’ve thought that the aching could be caused by either overuse (comparatively speaking) or by biomechanical processes since the muscles are attached to RA-damaged joints via tendons. I can feel myself getting weaker as time goes on. In fact, muscle strength in RA patients can be reduced by up to 75% of normal (see this study from 1992). During a follow-up visit about one of my ankle surgeries a few years back, the orthopedic surgeon noted in my chart that my calf muscles were getting atrophied. I no longer have the strength to open jars, dig a hole, or even maintain extended use of a muscle on a given task. I began to wonder about the impact of rheumatoid arthritis on muscles.
While muscles haven’t been a primary research target, there have been a few studies about muscles and RA. As far back as 1951, researchers found that inflammation of arteries in muscle tissue was observed in RA patients. In a study of 350 RA patients in Spain, weakness, muscle atrophy, and muscle inflammation were commonly observed in those suffering from RA. A detailed research study by Helliwell and Jackson published in 1994 documented RA’s impact on muscle tissue. They concluded, “Although there is significant muscle wasting in RA, it is likely that reduction in strength is also attributable to joint deformity and pain leading to inhibition of grip directly and, indirectly, by arthrogenous muscle inhibition. Doubts remain about the quality of muscle in RA”. Arthrogenous refers to “starting from a joint”. In 1993, Young produced a model demonstrating the connection between joint damage and muscles.
In addition to biomechanical problems, it is entirely plausible that biochemical processes involved with RA may negatively impact muscle tissue. According to some researchers, RA related cytokines including IL-1 and TNF are involved with breaking down the protein in muscles. According to Rall, et al (1996), “Adults with RA have increased whole-body protein breakdown, which correlates with growth hormone, glucagon, and TNFα production.” They concluded…”And although progressive resistance training led to improved strength and functional status in patients with RA and in controls, we saw no changes in protein metabolism or hormone levels as a result of the training intervention among any of the groups of subjects.” In other words, muscle breakdown continued even in midst of exercise. This mirrors a study by a group from Finland who noted that exercise helped RA patients’ muscle strength but not bone density. In 1974, a group of researchers from Sweden noticed changes in the muscle tissue of RA patients. They stated, “It is emphasized that the type II atrophy must be the result of a more complex mechanism than simple ‘disuse’.”
My suspicions about the biochemical impact and connectedness to RA impacted joints are both confirmed in the research literature. The question then remains as to what may be done to stop or reverse the impact of RA on muscles. Some argue that RA patients should engage in regular exercise in order to maintain muscle tone (see Mayo Clinic, NCHPAD). In a 2003 review of research studies on the impact of exercise on RA patients, it was found that most studies demonstrated that exercise positively impacted muscle strength without negatively impacting pain or daily activities. These results are interesting to me personally because every time I try to engage in exercise or strenuous activity, I feel worse and daily activities are limited (see recent post). Regarding exercise, many experts now recommend, “If you can, you should; if you can’t, you shouldn’t.” (Dr. Borogini Health Central RA website).
The evidence is clear – rheumatoid arthritis does impact muscle tissue. But more research is needed to identify the specific causes and to develop long term solutions. Of course, a bona fide cure for RA would do the trick. Fortunately, there are still researchers seeking answers as attested to by the fact that funding is being provided to study muscles in RA patients (see recent grant award in the UK).