The purpose of this study is to evaluate the effectiveness of a percussive/massage therapy device (Theragun, CA) to improve pain and restore functional outcomes in acute lateral epicondylitis “tennis elbow.” Participants will undergo physical therapy for 6 weeks; one session per week will be conducted with a certified physical therapist. Half of the participants will be randomly assigned to use a percussive/massage therapy device during these sessions and at home. All participants will undergo physical exams and complete questionnaires. Researchers believe that using a percussive/massage therapy device as a part of a treatment plan can help improve pain and outcomes compared to when this medical device is not used.