The objective of this study is to evaluate the efficacy of prescription-grade Crystalline Glucosamine Sulfate (pCGS), as an add-on treatment to conventional therapy, compared to usual therapy alone, in patients with erosive osteoarthritis of the hand (EHOA).

This is a 6-months retrospective study including patients with concomitant gonarthrosis and EHOA, defined as the presence of central erosion in at least two interphalangeal joints. Eligibility criteria are symptoms duration for at least 3 months, with a global hand pain score ≥40 mm on a 0-100 Visual Analogue Scale (VAS) and a Functional Index for Hand Osteoarthritis (FIHOA) score ≥6. The participants are stratified into two groups based on whether or not pCGS, at the daily dose of 1500 mg, was added to the conventional therapy for hand osteoarthritis (HOA). The latter consists of education and training in ergonomic principles, exercise and the use on-demand of acetaminophen or oral non-steroidal anti-inflammatory drugs. Patients are evaluated at baseline, after 3 and 6 months. Primary outcome measures are the change from baseline to month 6 in VAS and in FIHOA score. Secondary outcomes are duration of morning stiffness, health assessment questionnaire (HAQ), medical outcomes study 36-item short form (SF-36), symptomatic drugs consumption and percentage of treatment responders, according to the OMERACT/OARSI criteria.

Inclusion Criteria:

• Erosive Hand Osteoarthritis, defined as the presence of the classical central erosion in at least two interphalangeal joints
• Treatment for at least 6 consecutive months with prescription-grade crystalline GS at the daily dose of 1500 mg in addition to the conventional therapy or with usual care alone.
• Symptoms duration for at least 3 months defined as global hand pain score superior to 40 mm on a 0-100 VAS and a FIHOA score of at least 6.

Exclusion Criteria:

• Medical history of any inflammatory joint disease, septic arthritis, previous articular fracture of the concerned joints, or the presence of any other rheumatic diseases that could cause secondary OA, such as hemochromatosis
• Concomitant therapy with SYSADOAs, other than pCGS, steroids by any route of administration and intra-articular injection of any joint with hyaluronic acid during the previous 6 months
• Concomitant treatment with intra-muscular or intra-venous bisphosphonates in the previous 6 months
• Contraindications or special warnings for pCGS presented in the data sheet.

The participants are stratified into two groups (pCGS Group and Control Group) based on whether or not prescription-grade crystalline GS treatment, prescribed for the actually approved indication of knee OA, was added to the conventional therapy. This stratification is based on regrouping patients with similar clinical characteristics at baseline.