To determine the ideal dose of PRP for lateral epicondylitis. To see if 2 PRP injections are better than a single PRP injection or a saline injection to improve function and pain in patients with lateral epicondylitis.

Is there greater clinical improvement in long term pain and function when patients receive two PRP injections instead of one? This is a double-blinded randomized controlled study to determine the ideal treatment regimen for treatment of chronic lateral epicondylitis (tennis elbow). The investigators will compare pain visual analog scale (VAS) scores and functional Disabilities of Arm, Shoulder, and Hand (DASH) Questionnaire scores of patients receiving a single PRP injection and two PRP injections.

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.

PRP is an effective treatment in reducing pain of chronic lateral epicondylitis. This study aims to prove there is greater clinical improvement in long term pain and function when patients receive two PRP injections instead of one.

Inclusion Criteria:

1. Lateral epicondylitis - diagnosed by orthopedic or sports medicine physicians / 2 separate examinations (examination at referral / confirmatory examination at time of injection)
2. Pain at the lateral epicondyle on direct palpation
3. Pain with resistive wrist extension and/or supination
4. No clinical findings at annular ligament, radiocapitellar joint, or PIN (posterior interosseous nerve syndrome)
5. No underlying bone pathology
6. Symptoms present for > 3 months
7. Visual analog score (VAS) that is >= 5/10
8. Last steroid injection > 3 months
9. Failed previous therapy (> = 4 weeks of strap, splint, cast, injection or any other accepted therapy without satisfactory pain or function)

Exclusion Criteria:

1. Age < 18 years
2. Pregnant
3. Symptomatic Carpal Tunnel syndrome on the affected side
4. History of cervical radiculopathy
5. History of Diabetes Mellitus, Rheumatoid Arthritis, hepatitis
6. Blood disorder
7. No immunocompromised patients (Human ImmunoDeficiency Virus, cancer, immunomodulator therapies)
8. Oral Nonsteroidal Antiinflammatory in the past 1 week or Steroid Drug use in the past 3 months
9. Participation in a workers' compensation program or planning to apply for the program and/or any ongoing, pending, or planned legal action as a result of elbow pain