INTRODUCTION:~Lateral epicondylitis (tennis elbow) is a frequent repetitive stress injury, affecting the common extensor muscles at the lateral humeral epicondyle. Lateral epicondylitis has a well-known spontaneous healing tendency. Still the prevalence of the chronic lateral epicondylitis is 1.4% in working populations causing significant occupational disability and financial burden.~Systematic reviews of the effectiveness of different treatment modalities for lateral epicondylitis present conflicting results. There are no consistent guidelines for management of the prolonged lateral epicondylitis. Progressive strengthening and stretching exercises as well as botulinum toxin type A injections have been suggested to be effective in treatment of chronic cases. However, there are only a few studies comparing different treatment modalities and botulinum toxin treatment have not been included in any of these.~The purpose of this study is to compare efficacy, feasibility and cost effectiveness of the botulinum toxin type A injections to active nine weeks strength training and stretching program in the treatment of the chronic lateral epicondylitis.~The main hypothesis is that the botulinum toxin type A injections may enable more rapid pain relief while strength training may provide better functional results and less relapses during the follow-up.~SUBJECTS AND METHODS:~A sample size of 120 participants with an equal drop-out rate of 15 % per group was determined in advance to detect a clinically significant 30 percentage points difference in outcome measures between the treatment groups with the minimum success rate of 65 % at the statistical significance level of 0.05 and power of 80 %.~During the recruitment process all patient newly referred to Department of PM&R outpatient clinics in the Seinäjoki Central Hospital due to elbow pain are evaluated by the study investigators. Every eligible patient with written informed consent is recruited. A computerised random number generator is used to draw up an allocation schedule. Patients are allocated in treatment groups via opaque sealed envelopes marked according to the random schedule.~Measurements and training instructions are performed by five trained physical therapists. In addition to detailed personal training instructions given by physical therapist, illustrated instructions as well as instruction video will be provided for patients in the training group. Physical therapists instructing patients do not perform any measurements to enable blinding of assessor. Measurement devices are calibrated regularly according to the manufacturers' recommendations and quality assurance measurements with test weights are performed on regular basis.~The principal statistical analysis will be done on an intention-to-treat basis. Repeated measures of ANCOVA and Cox Proportional Hazard Regression are planned to be used as primary methods. If there will be relapses, more advanced longitudinal models such as Generalised Estimating Equations and Random Coefficient Analysis will be used.
The purpose of this study is to compare efficacy, feasibility and cost effectiveness of botulinum toxin type A injections to active nine weeks strength training and stretching program in the treatment of the chronic lateral epicondylitis.~The main hypothesis is that the botulinum toxin type A injections may enable more rapid pain relief while strength training may provide better functional results and less relapses during the follow-up.