Platelet-rich plasma (PRP) injection is a procedure to inject a concentrated preparation of the patient's own platelets into an injured tendon, ligament, or joint. The platelets release growth factors that may promote tissue healing.
A blood sample (15–60 ml) is taken from the patient's arm. The blood is spun in a centrifuge to separate and concentrate the platelets. The resulting platelet-rich plasma is injected into the affected area under ultrasound guidance. Some protocols include leukocyte-rich PRP (LR-PRP) and others leukocyte-poor PRP (LP-PRP) depending on the indication. The procedure takes 30–45 minutes.
PRP is considered for chronic tendinopathies (tennis elbow, patellar tendinopathy, Achilles tendinopathy, gluteal tendinopathy), early knee osteoarthritis, muscle injuries in athletes, and plantar fasciitis. The evidence base is strongest for lateral epicondylitis (tennis elbow) and knee osteoarthritis.
Physiotherapy (the mainstay of treatment for tendinopathy), corticosteroid injection (faster relief but shorter duration and potential tendon damage), shockwave therapy, activity modification, and structured loading programmes.
Stop anti-inflammatory medication (NSAIDs) for at least one week before the procedure — they inhibit the platelet function that PRP relies on. Outpatient procedure.
Evidence suggests PRP provides modest, gradual improvement over weeks to months for certain conditions — particularly lateral epicondylitis (Level 1 evidence) and knee osteoarthritis (moderate evidence). For other conditions, evidence is still emerging.
Significant pain flare for 48–72 hours is common and expected — the growth factors cause local inflammation as part of the healing response.
Not all patients respond. Evidence is moderate for most indications.
Some protocols recommend two to three injections at weekly intervals.
Very rare — the patient's own blood is used.
From the injection. Rare with ultrasound guidance.
Theoretical risk of excessive inflammatory response.
No anaesthesia needed beyond local anaesthetic at the injection site. Some clinicians avoid local anaesthetic as it may inhibit platelet function.
Rest the affected area for 48–72 hours. Do NOT take anti-inflammatory medication for two weeks after (they counteract the PRP mechanism). Gentle rehabilitation from one week. Progressive loading from two to four weeks. Maximum benefit may take six to twelve weeks.
Review at four to six weeks to assess response. Repeat injection at six to twelve weeks if needed.
The strongest evidence supports PRP for lateral epicondylitis (tennis elbow) and intra-articular PRP for mild to moderate knee osteoarthritis. For other conditions (Achilles tendinopathy, rotator cuff tears, muscle injuries), the evidence is promising but less definitive. Research is ongoing.
PRP works by delivering concentrated platelets that release growth factors and trigger a healing inflammatory response. Anti-inflammatory drugs suppress this response, potentially negating the benefit of the PRP.
PRP is not widely available on the NHS due to variable evidence. It is commonly available privately. NICE guidelines are evolving as more evidence becomes available.