The study will be conducted at Kaiser Modesto Sports Medicine involving 532 patients who meet strict criteria for chronic lateral epicondylitis (including greater than 2 months of chronic lateral epicondylitis and failing at least one other treatment modality). Patients are randomly divided between three groups: 234 patients will receive one PRP injection, 234 will receive two, and 64 in the control group will receive a saline injection. All participants will receive concurrent home based stretching and strengthening exercises. Results are to be measured using the Visual Analog Scale (VAS) and Disabilities of Arm, Shoulder, and Hand (DASH) Questionnaire on the initial and follow-up visits of 2, 6, and 12 months. Both measures have been validated by prior studies. Successful treatment of lateral epicondylitis will be defined as a 25% reduction in visual analog score VAS and DASH scores between initial and 6 month visits. Average control and experimental groups VAS scores are expected to be 8 out of 10 with an improvement to 7 and 6 respectively in 6 months. Average control and experimental group DASH scores are expected to be 49 with an improvement to 44 and 28 respectively in 6 months.