To assess the therapeutic efficacy, of the clinical response of intraarticular (IA) etanercept (E) 12.5 mg or placebo (P: NaCl) injections into single knee arthritic joint of patients with refractory knee joint synovitis (KJS), administered once every two week, for eight weeks, with cross over after 2 weeks, in two groups of randomly assigned patients, for whom traditional systemic disease-modifying antirheumatic drugs (DMARDs) is insufficient or inappropriate. The primary outcome measure is the Thompson articular index of KJS disease activity.