PURPOSE: Low-value imaging is associated with wasteful health care spending and patient harm. The routine use of magnetic resonance imaging (MRI) for the work-up of lateral epicondylitis is an example of low-value imaging. As such, our aim was to investigate the use of MRIs ordered for lateral epicondylitis, the characteristics of those undergoing an MRI, and the downstream associations of MRI with other care. METHODS: We identified patients aged ≥18 years with a diagnosis of lateral epicondylitis between 2010 and 2019 using a Humana claims database. We identified patients with a Current Procedural Terminology code corresponding to an elbow MRI. We analyzed the use and downstream treatment cascades in those undergoing MRI. Multivariable logistic regression models were used to assess the odds of undergoing an MRI, adjusting for age, sex, insurance type, and comorbidity index. Separate multivariable logistic regression analyses were used to determine the association between undergoing an MRI and the incidence of secondary outcomes (eg, receiving surgery). RESULTS: A total of 624,102 patients met the inclusion criteria. Of 8,209 (1.3%) patients undergoing MRI, 3,584 (44%) underwent it within 90 days after diagnosis. There was notable regional variation in MRI use. The MRIs were ordered most frequently by primary care specialties and for younger, female, commercially insured, and patients with more comorbidities. Performance of an MRI was associated with an increase in downstream treatments, including surgery (odds ratio [OR], 9.58 [9.12-10.07]), injection (OR, 2.90 [2.77-3.04]), therapy (OR, 1.81 [1.72-1.91]), and cost ($134 per patient). CONCLUSIONS: Although there is variation in the use of MRI for lateral epicondylitis and its use is associated with downstream effects, the routine use of MRI for the diagnosis of lateral epicondylitis is low. CLINICAL RELEVANCE: The routine use of MRI for lateral epicondylitis is low. Understanding interventions to minimize such low-value care in lateral epicondylitis can be used to inform improvement efforts to minimize low-value care for other conditions.