The purpose of this study is to determine whether a single injection of Dysport with a new protocol at forearm is effective in the management of chronic lateral epicondylitis.

Some studies valued the effectiveness of botulinum toxin. There is a great amount of controversy on the amount of botulinum toxin injected and the location of the injection. The purpose of the study is to compare the effectiveness of botulinum toxin injection with placebo at a new injection site at the forearm in the treatment of chronic tennis elbow unrelieved by corticosteroid injection and physiotherapy. It is a double blind randomized controlled trial.

Inclusion Criteria:

• Pain: pain will be assessed as the physician touches lateral epicondyle or passively flexing the patient's wrist and while the patient extends his/her wrist or 3rd finger against resistance. Individuals who fulfill two or more of above will be considered to have lateral epicondylitis.
• Symptom duration: should be at least 6 months.
• Previous trial of complete course of physiotherapy and corticosteroid injection.

Exclusion Criteria:

• Rheumatoid arthritis
• Generalized polyarthritis
• Local elbow arthritis
• Simultaneous medial epicondylalgia
• Bilateral lateral epicondylitis
• Neurologic deficits (abnormal light touch sensation, deep tendon reflexes abnormality, radicular pain, radial nerve entrapment, signs of nerve root compression, decreased muscle force, multiple sclerosis, seizures)
• The use of corticosteroid in last 30 days
• Simultaneous use of drugs other than acetaminophen or physical therapy in the course of study
• Pregnancy
• Breast-feeding
• Previous hand surgery
• Having a hobby or job that needs finger extension