The elbow is a complex joint made up of three bones, three joints, and three ligaments. Repeated microtraumas can lead to ligament injuries and instability, tendon damage, or degenerative processes affecting the bones, cartilage, and bursae. As a result, elbow pain is not uncommon, and diagnosing the underlying problem is not always easy. One reason for this is the complex anatomy packed into a small space. Many disorders produce overlapping symptoms, making them hard to tell apart. In this context, diagnostic confusion isn't unusual. So, posterolateral rotatory instability of the elbow has symptoms similar to those of lateral epicondylitis, the main diagnosis for a painful elbow, but the way it's treated is different.

However, a wrong diagnosis can be linked to treatment failure risks that might put the patient in a therapeutic, social, or work/sports dead end. An accurate and early diagnosis could allow for quickly setting up a treatment strategy suited to the condition.

The relationship between posterolateral elbow instability and lateral epicondylitis has been little studied in the literature. This project is based on the hypothesis that lateral epicondylitis is often associated with posterolateral instability. Checking the lateral collateral ligament of the elbow during scheduled surgery to treat lateral epicondylitis, either arthroscopically or openly, could help better assess this relationship.

The main aim of this study is to figure out the percentage of patients with posterolateral elbow instability, diagnosed either through arthroscopy or open surgery, among those with lateral epicondylitis who are up for surgery.

Inclusion Criteria:

• Patient, male or female, over 18 years old.
• Patient who has had pain in the lateral compartment of the elbow and has received well-managed medical treatment (splint, injection) for at least 6 months.
• Patient scheduled for planned elbow surgery, either arthroscopic or open.
• Patient with tenderness in the lateral epicondyle area.
• Patient experiencing pain at the lateral epicondyle during resisted wrist extension.
• Patient enrolled in or receiving benefits from a social security program.
• Patient has been informed and does not object to this research. ...

Exclusion Criteria:

• Patient with a history of elbow surgery, dislocation, or fracture.
• Patient with elbow deformities.
• Patient with synovial plica.
• Protected patient: adult under guardianship, curatorship, or other legal protection, deprived of liberty by judicial or administrative decision.
• Pregnant, breastfeeding, or laboring woman.
• Patient hospitalized without consent.

Patients with lateral epicondylitis of the elbow who require surgical treatment are referred to the orthopedics departments of Jean Mermoz Private Hospital and the Surgical Institute of the Hand and Upper Limb - ICMMS. Patients scheduled for this type of surgery and who meet the eligibility criteria will be offered the opportunity to participate in the study by the orthopedic surgeon during the pre-operative consultation. If inclusion hasn't taken place during the pre-op consultation, it can happen the day before the surgery.