USEFULNESS (overall rating): 3/5

PRP injections involve drawing some of your own blood (usually 1-2 tubes) which is then spun down to yield increased concentrations of platelets. Platelets are a crucial component of blood important in healing, and they contain growth enhancing factors thought to increase healing. The plasma is then injected into the area of damage at the lateral epicondyle.
PRP is being used on a wide variety of joint, tendon, and muscle conditions. There are various types of products, and more recent research suggests the type with leukocyte rich PRP appears to be more effective.
Sources:
Krogh TP, Bartels EM, Ellingsen T, Stengaard-Pedersen K, Buchbinder R, Fredberg U, Bliddal H, Christensen R. Comparative effectiveness of injection therapies in lateral epicondylitis: a systematic review and network meta-analysis of randomized controlled trials. Am J Sports Med. 2013 Jun;41(6):1435-46. doi: 10.1177/0363546512458237.
Studies suggest that PRP injections can be helpful but should be tried after more conservative approaches have been tried first. Some authorities believe it should be reserved for severe chronic cases before surgery is considered. Effects are usually not apparent at 12 weeks but are more significant at 24 weeks.
Sources:
Mishra AK, Skrepnik NV, Edwards SG, Jones GL, Sampson S, Vermillion DA, Ramsey ML, Karli DC, Rettig AC. Efficacy of platelet-rich plasma for chronic tennis elbow: a double-blind, prospective, multicenter, randomized controlled trial of 230 patients. Am J Sports Med. 2014 Feb;42(2):463-71. doi: 10.1177/0363546513494359.
Sanders TL, Kremers HM, Bryan AJ, Ransom JE, Smith J, Morrey BF. The Epidemiology and Health Care Burden of Tennis Elbow: A Population-Based Study. The American journal of sports medicine. 2015;43(5):1066-1071. doi:10.1177/0363546514568087.
Lateral Elbow Tendinopathy Development of a Pathophysiology-Based Treatment Algorithm Gev Bhabra,*† MD, FRCS(Orth), Allan Wang,†‡ FRACS, PhD, Jay R. Ebert,§ PhD, Peter Edwards,§ BSc, Monica Zheng,|| BPodM, and Ming H. Zheng,†{ PhD, MD, FRCPath. The Orthopaedic Journal of Sports Medicine, 4(11)