From National Institute of Arthritis and Musculoskeletal and Skin Diseases Spotlight on Research, September 2009
Although it is well understood that osteoarthritis causes progressive damage and pain to the knee joint, currently doctors do not have good data concerning which types of damage or location leads to various experiences of pain by patients. According to C. Kent Kwoh, MD, "Right now we don't have a good idea of what causes knee pain, and different people have various types of knee pain. The Knee Pain Map gives us a better way of describing different groups of people in terms of their knee pain and then getting a better understanding of what's causing it and ultimately how to cure it or help people manage it better."
Dr. Kwoh recently conducted a study to evaluate the impact a standardized process using a diagram of the knee allowing the interviewer to map the locations a patient indicates to be the focus of pain. The study included nearly 800 patients, and allowed interviewers to determine if pain in the knee was localized to any of seven areas in the knee, or regionalized to any of four larger (hand sized) areas of the knee, or if the patient was either unable to locate the pain in an area the size of their hand, or if the patient was unable to locate the knee pain it is termed to be diffuse.
The researchers found that participants with knee pain could identify pain locations and patterns and that trained examiners could reliably record the location of knee pain using the Knee Pain Map. "To our knowledge, this is the first study that allowed patients to either point to an area or cover a region that hurt, giving the patient the responsibility of identifying their pain as being in a specific location versus a more general region," Dr. Kwoh and his colleagues wrote in the journal Arthritis & Rheumatism.
“It is likely that there are several different causes and sources of pain, says Dr. Kwoh. While there are no nerve endings in the cartilage itself, the surrounding structures - including bone, joint lining, ligaments, etc. - do have nerve endings that may be sources of painful sensation, he says. Mapping the location of pain may eventually help doctors better understand the causes or sources of pain and how to treat them.
The next step will be to compare findings from patients' reports on the Knee Pain Map with x-ray and MRI findings collected as part of the Osteoarthritis Initiative (OAI), a public-private partnership between the NIH and private industry that seeks to improve diagnosis and monitoring of the progression of OA and foster development of new treatments. Nearly 5,000 people who have OA or are at risk of OA are participating in the OAI at four centers in the United States. In addition to x-ray and MRI scans, participants provide biological specimens (blood, urine, and DNA) and clinical data such as dietary intake, medication use and pain, function, and general health assessments.”