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All you need to know about PRP injections

What are PRP injections?

PRP stands for platelet rich plasma. PRP involves spinning a small sample of a patient’s blood to produce plasma that contains a concentrated amount of platelets, typically 4-6 x the normal number. The platelets are obtained through spinning the blood sample so the cells separate and the platelets can be extracted into a syringe.

Platelets are the cells within the body that are attributed to a number of healing processes. PRP has been shown to help stimulate the healing of chronically injured tissues, particularly useful in degenerative conditions such as osteoarthritis and tendinopathy.

PRP treatment involves the ultrasound-guided injection of platelets directly into the site of injury, to trigger the body’s healing mechanisms. The platelets have been shown to be a 100% natural method to trigger the regeneration of tissues.

What conditions can PRP treat?

PRP can be used to treat a number of chronic conditions. Research suggests PRP can be useful to treat:

  • Knee Osteoarthritis
  • Tennis Elbow
  • Golfers Elbow
  • Plantar Fasciitis
  • Rotator Cuff Tendinitis

How successful is PRP treatment?

PRP has been shown to be natural, safe and effective for treating early to mid-stage knee osteoarthritis. There are now 14 high quality research trials demonstrating the benefits of PRP treatment over placebo.

NICE have recently summarised the latest evidence on the use of PRP and recommend its use for mild to moderate knee osteoarthritis. Research studies have consistently shown on average a 70% reduction in pain and stiffness for early to mid-stage knee osteoarthritis with benefits seen at 6, 9 and 12 months after treatment.

What happens on the day of the appointment?

Appointments typically last 45 minutes. Firstly the practitioner will use diagnostic ultrasound to assess the area to be injected. The clinician will then draw blood from a vein in your arm. The blood will then be transferred to a specialist centrifuge where the spinning process will take place for 8 minutes. The PRP will then be drawn into a syringe and injected under ultrasound guidance into the affected area. If a tendon is to be injected then a local anaesthetic will be used to numb the area. If a joint is to be injected then local anaesthetic is not normally required. You will be asked to stay in clinic for 15 minutes after the injection to ensure no adverse reactions occur.

Will the injection hurt?

The procedure can be uncomfortable however local anaesthetic is often used during the treatment of tendinopathy to avoid any discomfort. Typically joint injections do not require local anaesthetic, as they are relatively painless.

What to expect after the injection?

It is common for the injection site to feel sore for 24-48 hours after the injection. It is also common for the injury to feel temporarily painful for 5-7 days after the injection – this is called a ‘post injection flare’. This is nothing to be concerned about and is a normal reaction to a healing process. This will pass within a few days and some analgesia such as paracetamol can be used as required.

It is important to make arrangements for driving because the joint or tendon can be painful after the injection making it impractical to drive home.

It is necessary to avoid strenuous activities for the first few days after the injection to avoid increasing the chances of post-injection pain. If a tendon has been injected then 7 days rest from all sporting activities is recommended.

How many injections will I need?

Research suggests that a course of 3 x injections at 1 x injection per month intervals is the optimum treatment protocol for osteoarthritis and tendinopathy. Clinical experience however dictates that if a discernable benefit has not been felt after 2 PRP injections then further injections are unlikely to benefit.

If you have been treated successfully with PRP in the past then future top-up treatments can be safely and effectively implemented. These cases will be discussed on an individual basis with your practitioner.

Possible risks and side effects

No serious side effects have been reported in the literature after the administration of PRP. The main side effect is pain after the injection however this is mostly seen after treating tendinopathy and not typically joint pain. Other side effects are very rare but discussed below.

  • Joint and soft tissue infections: this is extremely rare (1 in 50,00) and all necessary precautions are taken by the practitioner to minimise this.
  • Post-injection pain: fairly common but settles within a few days as discussed previously.
  • Minor bruising at injection site: usually very minor.

Are there any conditions that contra-indicate PRP?

  • Haemophiliac Disorders/taking anti-coagulant medication
  • Administration into Joint Replacements
  • Infection of the area to be treated
  • Pregnancy or if you are breast feeding
  • Active Cancers/Malignancy


Cook, C.S. and Smith, P.A., 2018. Clinical update: why PRP should be your first choice for injection therapy in treating osteoarthritis of the knee. Current reviews in musculoskeletal medicine, 11(4), pp.583-592.

Paterson, K.L., Hunter, D.J., Metcalf, B.R., Eyles, J., Duong, V., Kazsa, J., Wang, Y., Buchbinder, R., Cicuttini, F., Forbes, A. and Harris, A., 2018. Efficacy of intra-articular injections of platelet-rich plasma as a symptom-and disease-modifying treatment for knee osteoarthritis-the RESTORE trial protocol. BMC musculoskeletal disorders, 19(1), p.272.

Spaková, T., Rosocha, J., Lacko, M., Harvanová, D. and Gharaibeh, A., 2012. Treatment of knee joint osteoarthritis with autologous platelet-rich plasma in comparison with hyaluronic acid. American Journal of Physical Medicine & Rehabilitation, 91(5), pp.411-417.