The short answer. Athletes use platelet-rich plasma (PRP) and cell therapies such as bone marrow concentrate to help muscle, tendon and ligament injuries heal. Studies have found that athletes treated with PRP for acute muscle injuries returned to sport faster (8.6 days sooner in one review of hamstring trials) and, in another review, had a lower risk of re-injury1,2,3. The World Anti-Doping Agency (WADA) says PRP is not prohibited, and that non-transformed stem cells used alone to heal an injury are not prohibited as long as they return function to normal and do not enhance it4.
Much of the publicity around PRP has been about acute sports injuries, such as muscle and ligament injuries. PRP has been used to treat professional athletes with pulled hamstrings and knee sprains, and some athletes have credited it with a faster return to competition5. The American Academy of Orthopaedic Surgeons (AAOS) says treatment with PRP could hold promise5.
Injuries like these have typically been treated with medications, physical therapy or even surgery5.
Blood is mostly liquid plasma, with red cells, white cells and platelets suspended in it. Platelets are best known for clotting, but they also contain hundreds of proteins called growth factors that are important in the healing of injuries5. PRP is plasma with many more platelets than usual, and the concentration of platelets, and so of growth factors, can be 5 to 10 times greater5.
To make it, blood is drawn from the patient, and the platelets are separated from the other blood cells and concentrated by spinning the blood in a centrifuge. The platelets are then injected into the injured area5. Laboratory studies have shown that the higher concentration of growth factors may speed up the healing process5. Our guide to PRP explains the preparation in more detail.
A few practical points from AAOS5:
AAOS lists several factors that can influence how well PRP works: the area of the body being treated, the patient's overall health, whether the injury is acute or chronic, and how the PRP is prepared, including its cellular makeup5.
Three reviews published in 2026 pooled randomized trials of PRP for acute muscle injuries, and each reported a result in favor of PRP1,2,3:
| Review | What was pooled | What the review found |
|---|---|---|
| Nakagawa 2026 [1] | 6 randomized trials, 277 patients, acute hamstring injuries [1] | Return to play in an average of 21.4 days with PRP versus 30.0 days in the comparison groups [1] |
| Bensa 2026 [2] | 9 randomized trials, 474 patients, acute muscle injuries [2] | Faster return to sport with PRP (mean difference 7.5), plus greater pain relief in the hamstring trials [2] |
| Kobayashi 2026 [3] | 8 systematic reviews, acute muscle injuries [3] | Lower re-injury risk with PRP, rated high certainty [3] |
The Nakagawa authors concluded that PRP may shorten return to play after an acute hamstring injury, especially when the injection is image-guided1. In the Bensa review, the faster return held in the hamstring trials alone, and a statistical fragility analysis supported the return-to-sport benefit2. The Kobayashi review concluded that the current evidence supports selective use of PRP in sports settings, particularly for high-performance athletes at risk of a repeat injury3.
Our torn hamstring guide covers injury grades and typical recovery times.
AAOS says recent research has shown that certain tendon problems can have improved outcomes with PRP injections5.
Elbow ulnar collateral ligament (UCL) tears in throwers. In one case series, 23 athletes with a first-time partial UCL tear were treated with two PRP injections two weeks apart, plus bracing, physical therapy and a structured throwing program. They were released to play at six weeks. Twenty-two of them (96%) returned to play at the same or a higher level of competition without further intervention, and repeat MRI showed the ligament had reconstituted7. Because of the timing of sports seasons, the mean time back to competitive play was 82 days7. The authors concluded that the two-injection regimen is a safe and effective treatment for partial UCL tears7.
A second series looked at 34 baseball players with partial or complete UCL tears confirmed by MRI. They were treated with ultrasound-guided needling of the ligament followed by a PRP injection8. Twenty-six of 30 returned to sport at their pre-injury level within six months, at an average of 12.4 weeks. Average pain scores improved from 53.5 to 17.2, and average scores on the DASH sports module (a measure of arm disability) improved from 81.7 to 24.28. The authors concluded the technique can be an effective option for both partial and complete tears, and that for complete tears it may allow more athletes to avoid surgery and return to play faster8.
ACL reconstruction. A 2026 meta-analysis of 11 randomized trials (583 patients) found less knee laxity at 3 and 6 months when PRP was added to anterior cruciate ligament reconstruction with a hamstring tendon graft9. The authors described potential short-term benefits, including less laxity and improved radiological findings9.
A review of cell therapy for tendon problems found 22 studies with 658 patients10. Almost all of the studies showed the injections were safe during follow-up, with no serious side effects or immune reactions and only a few minor side effects10. The included studies showed that cell injections were effective in tendon problems at several sites: the rotator cuff, elbow, patellar tendon, Achilles and gluteal tendons10.
The authors concluded that cell therapy showed promising results and that the available evidence suggests it is safe at several sites of tendon disease10.
Bone marrow concentrate can also be added during surgery. In a randomized trial of 91 patients having arthroscopic repair of a torn supraspinatus tendon (part of the rotator cuff), bone marrow was drawn from the iliac crest, concentrated and injected at the repair site11. On MRI at one year, 18% of the shoulders treated with bone marrow concentrate showed a retear, compared with 57% of those treated with repair alone11. The authors concluded that adding bone marrow concentrate may result in a structurally superior repair11.
Regenerative medicine therapies, including stem cell products, are not yet FDA approved for orthopedic conditions12. Our post on stem cell injections covers the product types and what to ask a clinic.
At our practice, BMAC is performed at the Pueblo Surgery Center, a free-standing, AAAHC-accredited outpatient facility at the same address as the office. The marrow is drawn, processed and delivered in one visit, under light anesthesia so there is no discomfort during the harvest.
WADA's answers, from its own Prohibited List page:
The 2026 list took effect on January 1, 202613. WADA's stem cell answer covers cells used alone, with nothing added4. If you compete in a tested sport, confirm with your governing body or anti-doping organization before any injection.
Some injuries need an operation. AAOS gives the example of an athlete with a completely torn Achilles tendon, who may require surgery to repair it, and notes that healing of the repaired tendon can possibly be improved by treating the area with PRP during surgery5. Bone marrow concentrate can be added during surgery too, as in the rotator cuff trial above11.
At our practice, physical therapy and viscosupplementation come first. When they have not worked, PRP, BMAC or the two combined may be considered. Not every patient is a candidate, and a proper orthopedic evaluation is essential. Candidacy is decided at a consultation, before any financial commitment. Patients outside the area can have the first consultation and follow-ups by telemedicine, with imaging sent by email.
If you are in the Santa Barbara area, Dr. Scheinberg can examine the injury, review any imaging and talk through the options. See sports injury treatment or call (805) 682-1394.
Short answers to the questions patients ask most.
Have a question about your own situation?
Call (805) 682-1394No. WADA says PRP is not prohibited, and drawing blood to prepare and re-inject PRP is permitted. Individual growth factors from other sources remain banned4.
Under WADA's current answer, non-transformed stem cells used alone to heal an injury are not prohibited, provided they restore normal function and do not enhance it4. Check with your sport's anti-doping organization first.
In one series of throwing athletes with a first-time partial tear, 22 of 23 returned to play at the same or a higher level after two PRP injections combined with bracing, physical therapy and a throwing program, and repeat MRI showed the ligament had reconstituted7. In another series, 26 of 30 baseball players returned to their pre-injury level within six months8.
Reviewed by Dr. Richard Scheinberg, MD, a board-certified orthopedic surgeon in Santa Barbara with 40 years of surgical experience.
