The results of past studies of associations between crepitus and arthritis have been conflicting, with some indicating a strong likelihood that someone whose knees pop also has underlying arthritis and others showing little consistent relationship. Many of these studies, however, looked at people’s knees at one point in time, leaving the fundamental relationship between crepitus and the onset of arthritis, especially over the years, in doubt.
So for the new study, which was published this month in Arthritis Care & Research and funded primarily through the National Institute of Arthritis and Musculoskeletal and Skin Diseases, part of the National Institutes of Health, a group of researchers from the Baylor College of Medicine in Houston and other institutions decided to focus on the long-term health and creakiness of the knees of almost 3,500 participants in the ongoing Osteoarthritis Initiative.
This large-scale, national study has enrolled thousands of adults at risk of developing arthritis because of their age, body mass or other factors. (Being older than 45 or overweight greatly increases the likelihood of knee arthritis.) These men and women have visited a lab annually for at least four years for a knee X-ray and an exam that includes questionnaires about joint pain and how often, if ever, their knees creak, grind and pop.
The researchers now chose records about people who had not yet developed full-on knee arthritis, which the scientists defined as having both frequent knee pain and an X-ray showing bone spurs. People included in the new study could have a spur-riddled X-ray but little or no knee pain or a badly aching knee with a clear X-ray, but not both. The researchers also checked to see whether these people reported instances of crepitus sometimes or often.
Finally, they gathered the same information for a year after someone first had joined the original study and again at the end of four years. Then they compared the state of people’s knees over that time and looked at the associations, if any, with crepitus.
Over all, most people’s knees did not worsen significantly, especially during the first year that someone was in the study. About 18 percent of the studied joints progressed from showing suggestions of arthritis — pain or a worrisome X-ray — to having the full spectrum of both aches and a spur-ridden X-ray.
Many of the people in that 18 percent also had reported having crepitus at the start of the study. The instance was especially large among people whose knees had shown X-ray evidence of arthritis but who had not reported much joint pain. In that group, crepitus was a clanging alarm; the creaks and pops strongly indicated that they would develop more severe knee disease after a year or four.
But that was not true for everyone with crepitus. For some, their…