Background Knee osteoarthritis (OA) is a degenerative joint disease causing symptoms in 12% of people over the age of 651. One of the inherent problems with efficacy assessment of pain medication was the lack of objective pain measurements. In recent years functional MRI (fMRI) has emerged as a useful means to objectify brain response to painful stimulation2.
Objectives The aim of the present fMRI study was to objectively identify the effects of 4-month Condroitin Sulfate (CS) treatment on the brain response to pressure painful stimulation in patients with knee OA.
Methods This is a phase IV, randomized, double-blind clinical trial in which patients received CS 800 mg/day (Condrosan®, Bioiberica) or placebo for a 4-month treatment course. 64 patients were randomized and 49 were evaluable (27 in placebo and 22 in CS). Patients were assessed at baseline and post-treatment. Two tests were conducted in each session by applying adjusted painful pressure on patella surface and on knee medial interline during acquisition of two 6-min fMRI sequences. The main outcome measurement was attenuation of the response evoked by knee painful stimulation in the pain-processing brain system.
Results Patients receiving CS showed a tendency to report reduced subjective pain after treatment during patella pressure test (p=0.077) but no significant group by session interaction was demonstrated. fMRI of patella pain showed a larger activation reduction in CS group than in placebo in a posterior mesencephalon region including the periaqueductal gray (PAG). The entire PAG cluster (238voxels) with significant interaction showed a pre>post-treatment difference at p<0.05. In this paired analysis, CS group showed significant activation reduction in primary somatosensory cortex and extending to primary motor cortex and posterior supplementary motor area. Group by session interaction consistently revealed a tendency for this cortical change to be larger in the CS than in placebo (peak interaction x=2, y=-6, z=72; t=2.96, p=0.002 and 43 voxels-subthreshold- with p<0.01). No effects of CS were detected using the knee interline pressure test.
Conclusions The study succeeded in primary objective as a significant effect was demonstrated showing attenuation of brain response to painful pressure in key regions of pain-processing network using patella test. Despite knee medial interline is one of the most tenders points in patients with knee osteoarthritis, the pain generated by pressing down the patella surface, is probably less complex, and may be more selectively related to sensitization processes in the bone and the junction between bone and cartilage3. The observed positive effect of CS is consistent with the known CS action on cartilage protection.
Dillon CF, Rasch EK, Gu Q, Hirsch R. Prevalence of knee osteoarthritis in the United States: arthritis data from the Third National Health and Nutrition Examination Survey 1991–1994. J Rheumatol 33, 2271–9.
Schweinhardt P, Lee M, Tracey I. Imaging pain in subjects: is it meaningful? Curr Opin Neurol 19, 392-400.
Felson DT. The sources of pain in knee osteoarthritis. Curr Opin Rheumatol 17, 624-8
Disclosure of Interest None declared
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