BACKGROUND Withania somnifera (Linn.) Dunal (Solanaceae) has long been used as an herb in Ayurvedic and indigenous medicine and has received intense attention in recent years for its chemopreventive properties. OBJECTIVE The present study focuses on the effect of W. somnifera root powder on the behavioral and radiological changes in collagen-induced arthritic rats. METHODS The rats were randomly divided into five groups: normal control, arthritic control, arthritic rats treated with W. somnifera root powder (at dose levels 600 and 800 mg kg⁻¹) and arthritic rats treated with methotrexate (at dose level 0.3 mg kg⁻¹). The treatment with W. somnifera (daily) and methotrexate (weekly) was initiated from the 20th day post collagen immunization and continued up until the 45th day. Arthritis was assessed macroscopically by measuring paw thickness, ankle size and body weight. Arthritic pain was assessed by toe-spread and total print length of the affected paw. Functional recovery due to the oral treatment of W. somnifera and methotrexate was assessed by sciatic functional index and rota rod activity. RESULTS Administration of W. somnifera root powder (600 mg kg⁻¹) to the arthritic rats significantly decreased the severity of arthritis by effectively suppressing the symptoms of arthritis and improving the functional recovery of motor activity and radiological score. CONCLUSIONS W. somnifera root has a protective effect against collagen-induced arthritis (CIA) in rats. The results suggest that W. somnifera root powder acts as an anti-inflammatory and antioxidant agent in decreasing the arthritic effects in collagen-induced arthritic rats.