Inclusion Criteria:  At least 18 years of age Diagnosed lateral epicondylitis Receive a first ACP treatment at the Schulthess Klinik Signed informed consent form  Exclusion Criteria:  Lack of German language skills, which make it impossible to complete the questionnaire Diseases or conditions that would prevent accurate evaluation (e.g. central neurological, psychiatric or metabolic diseases) Legal incompetence Recent operations on the elbow or hand (less than three months ago)