Platelet-Rich Plasma (PRP) and Injection Therapies Info Evidence

What it is

Platelet-rich plasma, or PRP, is a treatment made from your own blood. A sample of your blood is processed to concentrate the platelets, which are the tiny cells that help with healing. This concentrated mix is then injected into the area that needs help.

Your doctor may consider PRP for a few different problems. For wear-and-tear arthritis in the knee, at least two injections are recommended, and the effects can last for at least 24 weeks [1]. It is also used for some tendon problems, such as tennis elbow (the sore spot on the outside of your elbow). For muscle injuries in sport, PRP is used selectively in some settings [2]. It is not used everywhere, though. Current evidence does not support it for Achilles tendon problems or for pain around the outside of the hip [3] [4].

How it works is still being studied. Platelets release natural growth factors, which are chemicals that encourage the body to repair tissue. Research has found a direct relationship between the concentration of platelets used and the amount of relief people report [5]. Studies also show that different mixes of PRP may suit different stages of arthritis [6].

The evidence behind PRP varies depending on the condition. Some studies support its use, while others do not, and researchers agree that more work is needed to confirm who benefits most [7] [8] [9]. Your doctor will talk you through whether PRP makes sense for your specific problem.

Does it work?

The honest answer is that it depends on the problem being treated. For wear-and-tear arthritis in the knee, trials have found that PRP can help, whether the mix contains white blood cells or not [10]. Both mixes gave similar results, with no difference in how people felt or in side effects [11]. Adding hyaluronic acid, a natural lubricant found in joints, to PRP may give better pain relief and movement than PRP alone [12].

For tendon problems, the picture is mixed. For tennis elbow, the evidence conflicts. One trial found PRP gave better results than steroid injections at 6 and 12 months, though steroids worked better in the first few weeks [13]. But a pooled analysis of trials found PRP did not improve pain or function compared with a placebo injection [19]. Higher concentrations of platelets were linked to more relief [5]. But for Achilles tendon problems, PRP worked no better than a placebo injection [3].

There are also gaps in the evidence. For knee arthritis, some reviews of PRP research have been written in ways that make the results look more positive than they are [14]. For ACL reconstruction, adding PRP has not been shown to clearly improve recovery [15]. Researchers are still working out which PRP mix suits which stage of arthritis [6].

So PRP has real support for some conditions, weaker support for others, and no support for a few. Your doctor will talk you through where the evidence sits for your specific problem.

What are the risks?

PRP uses your own blood, so the risks are different from those of medicines or surgery. Still, there are things you should know before you decide.

The most likely effects are short-term ones at the injection site. You may notice pain, swelling or bruising where the needle went in. These usually settle over a few days. For knee arthritis, studies that tracked side effects found no difference between the two main PRP mixes, and no difference in treatment failures [11]. Trials of PRP injections into the knee reported clinical benefits over 12 months and found the treatment was safe [16].

Some risks depend on where and why you are having the injection. For tennis elbow, one trial found steroid injections worked better in the first few weeks and PRP better at 6 and 12 months [13], although a pooled analysis found PRP no better than a placebo injection [19]. That matters because it means the early period after a PRP injection may feel slower than the alternative. For Achilles tendon problems, PRP worked no better than a placebo injection [3], so having it there means taking on the risks without any proven benefit. For ACL reconstruction, the evidence is not strong enough to show that adding PRP improves recovery [15].

There are also honest limits in the research. Some reviews of PRP for knee arthritis have been written in ways that make the results look more positive than they really are [14]. For fractures that are slow to heal, much more study is needed before PRP becomes routine [17]. And for facet joint problems in the spine, long-term results are not yet known [8].

Your doctor will go through the specific risks for your condition and the area being injected. If you notice increasing pain, redness or warmth at the injection site after you go home, contact the practice for advice.

Is it right for you?

PRP tends to suit some problems better than others. For wear-and-tear arthritis in the knee, injections given over a 12-month period have been found to help and to be safe [16]. The mix used can be matched to how early your arthritis is, because different stages respond to different preparations [6]. People who play competitive sport and have arthritis in a large joint are one group where PRP is systematically offered [18].

For some conditions, the evidence does not back routine use. This includes pain around the outside of the hip [4]. For tennis elbow, a pooled analysis of trials found PRP worked no better than a placebo injection [19], although one trial found it did better than steroid injections at 6 and 12 months [13]. For ACL reconstruction, adding PRP has not been shown to clearly improve recovery [15]. By contrast, for chronic tenosynovitis, which is swelling of the tissue sheath around a tendon, one trial found PRP worked better than a placebo injection [20].

Where PRP sits against other options depends on your problem. For knee arthritis, the two main PRP mixes, with or without white blood cells, gave similar results [10] [11]. For tennis elbow, one trial found steroids worked better in the first few weeks and PRP better at 6 and 12 months [13], but pooled trials have not confirmed a benefit over placebo [19].

Choosing PRP is a shared decision with your doctor. It should fit your condition, your stage of arthritis and your goals. The risks section above sets out what to expect, including the short-term effects at the injection site. Ask questions before you decide, and make sure the plan makes sense for you.

The bottom line

PRP is worth considering for some problems and not others. For wear-and-tear arthritis in the knee, injections have been found to help and to be safe over a 12-month period [16]. For tennis elbow and Achilles tendon problems, and for pain around the outside of the hip, the evidence does not back routine use [19] [3] [4]. Set your expectations accordingly: relief tends to build over weeks to months rather than days, and for knee arthritis the effects can last for at least 24 weeks [1]. The most important caveat is that the research is uneven, and some reviews of PRP for knee arthritis have been written in ways that make the results look more positive than they really are [14]. Talk it through with your doctor before you decide.

Platelet-Rich Plasma (PRP) and Injection Therapies Info Evidence

What it is

Does it work?

What are the risks?

Is it right for you?

The bottom line

Overview

How It Works

Osteoarthritis

Tendinopathy

Muscle Injuries

Fracture Healing

General Considerations

What the Evidence Shows

Knee Osteoarthritis

Tendinopathy and Epicondylitis

Other Musculoskeletal Indications

Methodology and Research Gaps

Practical Considerations

Dosing and Protocol Optimization

Leukocyte Content and Preparation

Indication-Specific Efficacy

Research Gaps and Methodological Considerations

Key Evidence

References