Doxycycline for Elbow Tendinopathy

Inclusion Criteria: * Males and females ages of 18 and up * Atraumatic unilateral elbow pain of ≥ 6 weeks duration * Diagnosed clinically as lateral or medial elbow tendinopathy * Activity-related lateral or medial elbow pain * Tenderness of the lateral or medial epicondyle * Pain with gripping and/or resisted wrist extension with the elbow extended * Pain with passive wrist flexion and finger with the elbow extended * Internet access to complete electronic surveys Exclusion Criteria: * Prior surgery of the affected elbow * Prior injection of the affected lateral or medial epicondyle or extensor tendons * Prior extracorporeal shockwave therapy to the affected elbow * Suspicion for radial tunnel syndrome (tenderness distal to the lateral epicondyle in the area of the supinator muscle dorsally, pain with resisted supination with the elbow extended, and/or weakness of the extensor digitorum communis) * Separate upper extremity injury or condition that would interfere with full participation in the home exercise program * Fluoroquinolone-associated tendinopathy * Ligamentous laxity on exam * Evidence of osteoarthritis or osteochondral lesion on radiographs * Autoimmune condition * Pregnant, intend to become pregnant, or breastfeeding * Premenopausal women who are not using contraception * Allergy to doxycycline or other tetracyclines * Current esophagitis or peptic ulcer disease * Current use of medication for which there is a drug interaction with doxycycline * Who do not spe…