Cartilage loss linked to only slightly worse knee OA pain
Click Here to Manage Email Alerts
Loss of cartilage thickness is associated with only a modest increase in knee osteoarthritis pain, an effect mediated in part by worsening synovitis, according to findings published in the Annals of the Rheumatic Diseases.
“There is an indirect path by which cartilage loss could affect pain,” David Felson, MD, of Boston University, and colleagues wrote. “The relationship could be through structures within the knee now widely thought to cause pain because of their rich nociceptive innervation, the synovium and bone marrow.”
“Since cartilage loss co-occurs with synovitis and bone marrow lesions (BMLs) in OA, in cross-sectional analyses the latter two lesions could confound an association of cartilage loss with pain,” they added. “In longitudinal studies, an effect of cartilage loss on pain could be due to the intermediate effect of cartilage loss promoting synovitis or BMLs, which then cause pain. Such a relationship would be described as mediation.”
To analyze the link between cartilage loss and worsening knee pain, after adjusting for bone marrow lesions and synovitis, and whether said pain is mediated by worsening synovitis, Felson and colleagues analyzed data from the Osteoarthritis Initiative. Specifically, the researchers included 600 participants with, or at risk for, OA who were selected for a case–control study nested within the Osteoarthritis Initiative. They scored MRIs for these participants at baseline, 12 months and 24 months for quantitative and semiquantitative measures of OA structural features.
The researchers focused on change in medial cartilage thickness, and used linear models to calculate mean changes in Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain score with cartilage loss. They adjusted the results for baseline bone marrow lesions, synovitis and covariates. Felson and colleagues performed subanalyses for knees with non-zero baseline WOMAC pain scores and another for non-valgus knees.
According to the researchers, loss of cartilage thickness was significantly associated with a small degree of worsening knee pain over 24 months. Specifically, a loss of 0.1mm of cartilage thickness over 2 years was associated with a 0.32 increase in WOMAC pain. The link between cartilage thickness loss and pain was mediated by synovitis change, but not by changes in bone marrow lesions. The researchers reported similar results in the sub-analyses.
“This study suggests that it may be nearly impossible to develop a drug that both reduces cartilage loss and relieves pain in osteoarthritis, especially if the target for the drug is to protect cartilage,” Felson told Healio Rheumatology. “We found that cartilage loss does not cause much pain at all, so that preventing it probably would not alleviate much pain.”
Collapse
Read more about
Click Here to Manage Email Alerts