The study aims to evaluate the effectiveness of Blood Flow Restriction Training for the treatment of lateral elbow epicondylopathy.

1. To test a non-invasive, rapid treatment option for epicondylopathia humeri radialis for its effectiveness, Blood Flow Restriction (BFR) training will be supplemented to the applied exercise therapy. In BFR training, blood flow to the muscle is reduced by tying off the limb to be trained, e.g. with a blood pressure cuff, to achieve mechanical compression of the underlying blood vessels. This results in increased accumulation of blood in the capillary bed distal to the pressure cuff. Although isolated adverse effects have been reported, based on the current literature, it can be assumed that BFR training is comparable to conventional training in terms of safety for the user. Regarding the effect of BFR applications, it has been shown that even BFR without additional training measures can reduce muscle atrophy occurring during immobilization. A systematic literature review confirmed the positive effect of BFR augmented strength training in terms of strength development as well as muscle gain. The first positive results of BFR training compared to conventional physiotherapy have already been shown in rehabilitation after replacement surgery of the anterior cruciate ligament and after treatment of a radius fracture. Therefore, there is a scientific interest to verify the effectivity of this method in another disease of the musculoskeletal system, epicondylopathia humeri radialis.

   Question: Does the implementation of a BFR-protocol in the physiotherapeutic treatment of epicondylopathia humeri radialis lead to a significantly pain relief and function improvement in the affected hand? Hypothesis: The implementation of a BFR-protocol in the physiotherapeutic treatment leads to a significantly pain relief an function improvement in comparison to a cohort without BFR.

2. All patients who meet the inclusion criteria will be informed about the study in the special consultation for shoulder and elbow diseases and asked whether they would like to participate and will receive a declaration of participation if they agree. Patients are informed in detail that participation is voluntary, and that non-participation will not result in any disadvantages for their treatment. Prior to the start of therapy, one of the above-mentioned study physicians will personally inform the patient about the risks and benefits of the study. After sufficient time for reflection, the corresponding declaration of participation is gone through with the patient, signed by both parties in case of consent and the patient receives a copy of it. After signing the participation form, an appointment will be made to start the six-week randomized physiotherapy (2x per week a 20min; group A: Physiotherapy + BFR while intermittently wearing the BFR cuff (Delfi Medical Innocation Inc., Vancouver, Canada) at 50% of arterial occlusion pressure analogous to previous studies; Group B Physiotherapy + sham-BFR (BFR cuff inflated to 20mmHg). Patients are informed that they can discontinue therapy without giving a reason.

Physiotherapy treatment will be performed according to the current evidence-based protocol in the Department and Polyclinic for Sports Orthopedics of the Klinikum rechts der Isar of the Technical University of Munich twice a week over a period of six weeks. Randomization will be done by the treating physiotherapist(s) before the first physiotherapy session. Before the start of the first therapy unit (T1), as well as after completion of the six-week intervention (T2), six weeks after completion of therapy (T3) and again 12 weeks aufter completion of the physiotherapeutic treatment (T4), both clinical examinations to assess the progress of therapy by a blinded study physician and the completion of a standardized questionnaire by the subject will take place. No travel or expense allowance is provided. During the clinical examination, the joint status as well as the clinical signs of epicondylopathia radialis humeri will be collected. Further data collection is performed by means of questionnaires.

Inclusion Criteria:

• diagnosis of lateral epicondylitis
• duration of symptoms > 6 weeks
• failed physical therapy
• absence of x-ray abnormalities
• written and informed consent

Exclusion Criteria:

• prior joint infiltrations
• duration of symptoms > 12 months
• concomitant rheumatoid diseases
• concomitant elbow pathologies, including medial epicondylitis
• concomitant radicular symptoms of the cervical spine, shoulder or hand
• traumatic etiology of symptoms

IPD is not shared due to strict data protection laws in Germany, such as the GDPR, which ensure the security of sensitive medical data. Sharing individual patient data poses significant risks to data security, particularly regarding unauthorized access or misuse. Additionally, explicit consent from participants is often missing for data sharing beyond the original research purpose. Without such consent, any disclosure would be legally impermissible and ethically problematic. Therefore, safeguarding privacy and complying with legal regulations are paramount.

The Participant is randomly assigned to a cohort by drawing a number. Only the attending physiotherapist knows which number belongs to which cohort and start then either the BFR-training or the sham-BFR. The examining doctor in the preliminary investigation and in the follow-ups does not know how the patients were treated. Also the outcomes assessor has no informations about the treatment of the patients, therefore the assessment of the results is also carried out blindly.