Trial of Blood Flow Restriction Plus Physical Therapy vs. Physical Therapy Alone for Lateral Epicondylitis

Inclusion Criteria: * The diagnoses included are lateral elbow pain, lateral epicondylitis, or lateral epicondylalgia, more general diagnoses elbow tendinitis or elbow pain will be included if their clinical picture at physical therapy meets criteria for lateral epicondylitis. * If the inclusion diagnosis is other than lateral epicondylitis or tennis elbow (such as elbow pain), we will confirm the diagnosis at the first therapy visit with tenderness at the lateral epicondyle and/or pain with resisted wrist/long finger extension at the lateral epicondyle. * Pain for 4 weeks or more. * All participants must be between the age of 18 and 70 years old and have had pain for 4 weeks or more. Exclusion Criteria: * Ligamentous elbow sprain, osteoarthritis of elbow and cervical radiculopathy in the affected limb will be excluded from the study. * Any history of ligamentous, bony or other soft tissue reconstruction surgery at the affected elbow, * Vascular disorders to include: history of DVT, history of endothelial dysfunction, peripheral vascular disease * Injection therapy (corticosteroid, platelet rich plasma, or other injection therapy) in the prior 3 months to the affected site * Current fracture in affected arm * History of crush injury to affected arm * Any surgery on affected arm in last 1 year * Surgical procedure on their contralateral extremity (Changed 9/2019 to surgery within last year on contralateral upper extremity). * History of lymphectomy (such as axillary exploration with breast surgery, lymph node biopsy in the affected axilla/arm) * Pregnancy * Active infection * Current cancer diagnosis/treatment * Sickle cell anemia or trait * Kidney dialysis * History of syncope/passing out with pressure to body (such as massage, or blood pressure cuff). * inability to consent