 This 6-month randomized, placebo-controlled, double blind trial will compare a single intra-articular IA injection of 100 units of Botulinum Toxin A BoNTA to placebo for improvement in pain, function and quality of life QOL, and safety in patients with painful total knee arthroplasty TKA. Patients will be recruited at the Minneapolis VA Medical Center. Patients will be eligible if they are over age 18, have TKA, have pain 610 on 0-10 numeric rating scale NRS and are not candidates for revision surgery. 