Expected Conclusion: No study to date has examined BTX-A as a treatment for basal joint arthritis. Some patients are not surgical candidates and are reliant on non-surgical treatments for pain control and maintenance of function. BTX-A has shown to be effective in treating osteoarthritis of larger joints that undergo frequent use, including cases resistant to steroid injections. The basal thumb joint also undergoes frequent use and is often resistant to steroid injection. We believe that BTX-A will provide another efficacious non-surgical option for treatment of the CMC joint of the thumb. We estimate that the study will require approximately three to four years to achieve adequate patient numbers for each group.