• Pain at 1 month assessed on visual analog scale is the main outcome measure.
  

• Disability at 6 months (Cochin Hand Function Scale) and deformation at 1 year are the main secondary outcome measures.
  

The prevalence of digital osteoarthritis varies according to whether a radiological or clinical definition is adopted. Radiologically defined osteoarthritis of the hand has been estimated to represent 38% of women and 24.5% of men over 66 years of age but higher prevalence of 60-70% has also been reported. Of patients with radiological signs, 20 to 40% become symptomatic. For patients over 55 years of age, the distal interphalangeal joints are the most prevalent site of osteoarthritis (20%) determined radiologically and clinically, followed by the base of the thumb (8%) and proximal interphalangeal joints (5%). This prevalence increases with age, and the incidence peaks in perimenopausal women. Osteoarthritis in the base of the thumb (BTOA) concerns the trapeziometacarpal joint, with a possible secondary location at the trapezotrapezoidial and scaphotrapezial joints. BTOA induces a closure of the first web, which in turn causes an alteration of the thumb-index pinch and therefore a limitation in hand function. Pain induced by the compression of the thumb column during pinching could also lead to functional disability. Effect of a simple intervention such as wearing rest thumb orthoses on pain and disability is unknown.