FORT LAUDERDALE, Florida—Pain in knee osteoarthritis (OA) is associated with changes in several characteristics that are identifiable on magnetic resonance imaging (MRI) and are reversible. According to Yuqing Zhang, MD, professor of medicine and epidemiology at Boston University School of Medicine, OA knee pain fluctuates in parallel with changes in synovitis, effusion, and bone marrow lesions (BMLs). Dr. Zhang reported these data from the Multicenter Osteoarthritis Study (MOST) of the Osteoarthritis Research Society International (OARSI) at the 2007 World Congress on Osteoarthritis.1

"We found that changes of synovitis, effusion, and BML were strongly associated with the fluctuation of knee pain. Since these MRI features are reversible, clinical intervention on these features, if possible, may help to reduce knee pain symptoms," Dr. Zhang said.

Which changes cause pain?

The MOST study is a longitudinal study of risk factors for knee structural changes pain in OA patients. Dr. Zhang said, "While pain in knee osteoarthritis has long been considered a chronic condition, the symptoms experienced by OA patients are neither constant nor stable, but rather fluctuate. These observations suggest that factors that vary over time within a person are responsible for pain fluctuation. Few studies have been conducted to examine the effect of time-varying factors on knee pain fluctuation."

"We found that changes of synovitis, effusion, and BML were strongly associated with the fluctuation of knee pain. Since these MRI features are reversible, clinical intervention on these features, if possible, may help to reduce knee pain symptoms."—Yuqing Zhang, MD.
The investigators in the study examined the association between changes in MRI features and changes in knee pain. Patients were asked about pain, aching, and stiffness on most days in the affected knee(s) at baseline and had knee MRIs at baseline and at one or two visits over a 30-month follow-up period. They were compared with controls without knee pain.

Synovitis was scored 0-3 in two sites (infrapatella and intercondylar), effusion was scored 0-3 for each knee, and BML's were scored 0-3 in nine subregions. Synovitis and BML scores within each knee were scored by totaling across the sites or subregions.

"We defined a visit as a case-visit if a knee had pain on most days of the past month prior to that clinic visit, and as a control-visit if the same knee did not have pain on most days of the past month prior to that clinic visit. The visits with no knee pain served as the controls for the case-visits of the same knee," Dr. Zhang said.

The researchers analyzed 250 knees (232 subjects) that had knee pain in at least one, but not all, clinic visits. They found that changes in synovitis, effusion, and BML scores were strongly associated with knee pain fluctuation.

Odds ratios (OR) of knee pain increased from 1 to 23.7 when synovitis score increased from 0 to 3-6 at the same knee (P for trend <0.001). ORs of knee pain increased from 1.9 to 9.2 for an increase in effusion score from 0 to 2-3 (P for trend <0.001). ORs of knee pain occurrence increased from 1 to 16.5 when the BML score increased from 6 to 13 (P for trend <0.001).

Reference

1. Zhang Y, Nevitt M, Niu J, et al. Reversible MRI features and knee pain fluctuation: the MOST study. Presented at: OARSI 2007 World Congress on Osteoarthritis; December 6-9, 2007; Fort Lauderdale, Fla. Abstract 5.