Does PRP work for tennis elbow? The placebo trials disagree

Whether PRP works for tennis elbow depends almost entirely on what it is measured against. Against a control injection, the pooled trials find no clear advantage. Against physiotherapy or shockwave treatment, one two-year trial finds a large one [1][3].

Tennis elbow is pain on the outside of the elbow, where the muscles that straighten the wrist attach to the bone. It affects 1% to 3% of adults a year [3].

A review that pooled 33 randomised trials of PRP for tendon problems, 2,025 people in all, included 8 trials in tennis elbow and found no clear difference between PRP and the comparison group in pain or in how well the arm worked [1]. That held under 3 months, at 3 to 6 months, and at a year or beyond [1].

The comparison injections were a mixed set: steroids, salt water, the patient's own unspun blood, local anaesthetic, and dry needling, which is needles inserted without injecting anything [1]. The reviewers graded every one of those comparisons low or very low certainty, meaning the underlying trials were too small or too open to bias for the answer to be trusted [1].

A second review read all 20 randomised trials of PRP for tennis elbow, 1,520 patients, and judged only 5 of them to be at low risk of bias [6]. Within those 5, three had a placebo group and only one found PRP ahead; two compared PRP against steroid injections and reported contradictory results; one compared it against an injection of the patient's own unspun blood and found the two about equal [6]. Only 8 of the 20 trials recorded what was actually in the PRP they injected [6].

The strongest single result is a 2025 trial in adults older than 35 whose elbow had hurt for more than 6 months and had not responded to at least 3 months of other treatment. Of 231 people enrolled, 202 finished. At 24 months the PRP group's disability score had fallen by 31.18 points, against 20.70 for prolotherapy, another injection treatment, 18.70 for physiotherapy and 17.62 for shockwave treatment, which aims pulses of pressure at the tendon from outside the skin [3].

That score comes from a questionnaire about trouble using the arm and hand, and a fall of 10 points is the smallest change patients actually notice, so all four groups cleared it [3]. Asked to rate their own satisfaction, patients scored PRP highest and physiotherapy lowest [3].

A 2025 trial split 91 people whose elbow had hurt for more than 3 months into PRP plus shockwave, a dummy PRP injection plus shockwave, or shockwave alone, with exercise therapy for everyone. The PRP group reported less pain during activity and at night at the 4-week and 12-week checks and had stronger hand grip by 12 weeks, but ultrasound scans of the tendon showed no difference between the groups [5].

A broader review that worked through 40 earlier pooled analyses came out in favour of injection treatments, PRP and the patient's own blood among them, and against shockwave therapy and acupuncture [2].

The idea is that platelets carry a repair kit. Platelets are the small cell fragments in blood that plug wounds, and their granules hold growth factors, which are proteins that tell cells to multiply, build new tissue and grow new blood vessels [7]. Concentrating them and injecting them into a damaged tendon is meant to restart a repair process that has stalled [9][11].

In the laboratory that story holds up. A review of 36 laboratory and animal studies found that PRP added to tendon and ligament cells made them multiply, move and produce more collagen, the fibrous protein tendons are built from, and that it raised the activity of the genes that make it [8]. In live animals it increased cell numbers and blood vessel growth in the tissue, with the clearest effect between the third and fourth week after treatment [8].

Some of the pain relief may have nothing to do with repair. One review describes PRP damping down inflammation by shifting immune cells towards a repair mode, and separately points to serotonin, a signalling chemical platelets carry, as a pain-dampening route [7]. Pain can fall without the tendon itself changing, which is roughly what the trial with the dummy injection saw when it scanned the tendon and found nothing [5].

The weak link is that nobody has pinned down what to inject. PRP is sorted by how many white blood cells it contains, how its fibrin scaffold is built, which is the mesh of protein strands that holds a clot together, and how concentrated the platelets are. Single-spin, double-spin and buffy-coat methods of spinning the blood, the buffy coat being the thin layer where platelets gather, each give a different product [7]. The same laboratory review that found positive effects also turned up studies where PRP did nothing or made things worse, and put the inconsistency down to that variability in preparation [8].

The certainty of this evidence is as much of a problem as its direction. The reviewers who pooled the tendon trials graded every comparison low or very low certainty [1], and the reviewers who read the 20 tennis elbow trials one by one found that blinding of patients and staff was done badly across the set [6]. A 2022 commentary puts it bluntly: PRP went into wide clinical use without passing through the dose-finding and approval steps a drug would, so the best preparation method and the right number of injections are still unknown [4].

The two-year trial that favoured PRP is the most quotable number on this page, and its entry rules were narrow. The result applies only to people who match them [3]:

• adults older than 35, not younger people
• elbow pain lasting more than 6 months, not a recent flare-up
• pain that had already failed at least 3 months of non-surgical treatment
• no corticosteroid or botulinum toxin injection in the recent past
• no complete tear of the extensor tendon, the tendon that straightens the wrist

Most of the papers on this subject are about other tendons. Of the 33 trials in the pooled review, 8 were in tennis elbow; the rest covered the Achilles tendon, the tendons around the shoulder, the kneecap tendon, the sole of the foot, and carpal tunnel syndrome, which is nerve compression at the wrist [1]. PRP did reduce pain in carpal tunnel syndrome in that same review [1], while a separate pooling of 4 placebo-controlled trials in 170 people with Achilles tendon pain found no benefit at 3, 6 or 12 months [14]. A result in one tendon predicts little about another.

One side effect was consistent: pain at the injection site was more common with PRP than with the injections it was compared against [1].

Longevity and regenerative-medicine clinics commonly list PRP among their injection services, usually alongside other blood-derived or cell-based treatments. The trials give a fair picture of what a first visit involves. In the 2025 four-arm trial, the diagnosis was made by physical examination plus an ultrasound scan of the elbow, and only people who had already tried at least 3 months of non-surgical treatment were enrolled [3]. Blood is drawn and spun in a centrifuge to separate out a platelet-rich layer, by one of the methods above, depending on the clinic [7], then injected, usually with ultrasound guiding the needle [1]. On how many injections, the trials do not agree: of the 33 tendon trials in the pooled review, 20 gave a single injection and 13 gave several [1]. Exercise therapy ran alongside the injection in both 2025 trials [3][5]. In the one with a dummy injection, every group did the exercises, that group included [5].