Background The Osteoarthritis Initiative (OAI) is the largest knee osteoarthritis (OA) observational cohort. It provides the possibility to study the evolution of OA structural changes over time and the associated risk factors. It also allows the potential disease-modifying OA drug (DMOAD) effects to be explored in patients over time.

Objectives To determine, using data from participants enrolled in the progression cohort of the OAI, the effects of existing meniscal extrusion on the extent of cartilage loss and structural changes over time, and response to pharmacological treatment including the combination of glucosamine and chondroitin sulfate (Glu/CS).

Methods Knee OA patients were stratified based on the presence/absence of medial meniscal extrusion at baseline and on whether or not they received conventional OA pharmacological treatment (analgesics/non-steroidal anti-inflammatory drugs [NSAIDs]) and/or Glu/CS for 24 consecutive months. The main outcomes were knee structural changes including the cartilage volume measured by quantitative magnetic resonance imaging (MRI) and of loss of joint space width (JSW).

Results Participants reported taking (+) (n=300) or not taking (−) (n=300) OA treatment (analgesics/NSAIDs). The participants with meniscal extrusion had more severe disease at baseline. In the −analgesics/NSAIDs group with meniscal extrusion, participants taking Glu/CS had significantly reduced loss of cartilage volume at 24 months in the medial tibiofemoral compartment (p=0.02) and lateral plateau (p=0.05). No effect of Glu/CS was observed in patients without extrusion. In the +analgesic/NSAIDs group without meniscal extrusion, those taking Glu/CS had significantly reduced loss of cartilage volume in the global knee (p=0.055), medial compartment (p=0.05), lateral plateau (p=0.007), and trochlea (p=0.04). No effect of Glu/CS treatment occurred in participants with extrusion. No significant reduction in JSW was found between those taking (+) and not taking (−) Glu/CS treatment.

Conclusions This study confirms that combined administration of Glu/CS has significant protective effects on structure in knee OA. The presence of meniscal extrusion was found to be an important factor that can influence the drug effect on cartilage volume. X-rays were found to be much less sensitive than MRI at documenting the protective effect of treatment on structural changes.

Disclosure of Interest : J.-P. Pelletier Shareholder of: ArthroLab Inc., Consultant for: Bioiberica, C. Roubille: None declared, F. Abram Employee of: ArthroLab Inc., P. Delorme: None declared, J.-P. Raynauld Consultant for: ArthroLab Inc., J. Martel-Pelletier Shareholder of: ArthroLab Inc., Consultant for: Bioiberica

DOI 10.1136/annrheumdis-2014-eular.2248