Chronic knee pain unresponsive to oral medications and intra-articular corticosteroids and viscosupplements is an important treatment problem, especially for the young, very old and those with complex medical problems that preclude joint reconstructive surgery. We hypothesized that intra-articular botulinum toxin could provide important joint pain relief in these patients. This is a prospective, double blined, placebo controlled 6month trial with an open label extension phase when pain returns to baseline levels (re-injection with 100units of botulinum toxin and 6 months followup thereafter.