Platelet-rich plasma (PRP) works by concentrating the healing components already present in your blood and delivering them directly to damaged tissue. A small blood sample is drawn, spun in a centrifuge to separate out a platelet-dense layer, and then injected into the treatment area. Those concentrated platelets release a cocktail of growth factors that stimulate cell repair, new blood vessel formation, and collagen production. The result is a treatment that essentially amplifies your body’s natural repair process.
What Happens Inside the Body
Platelets are best known for forming blood clots, but they also carry tiny storage compartments called alpha granules packed with growth factors. When PRP is injected into damaged tissue, the platelets activate and release these growth factors into the surrounding area. The key players include proteins that promote new blood vessel growth (VEGF), stimulate cell division in connective tissue (PDGF), trigger collagen production (TGF), and speed up cell maturation (IGF). Together, these signals recruit repair cells to the injury site, increase blood flow, and push fibroblasts and other structural cells to multiply and rebuild.
This isn’t introducing a foreign substance. It’s flooding an injury site with a concentrated version of what your body would normally send there on its own, just in much higher quantities. PRP typically concentrates platelets four to eight times above normal blood levels, which means a proportionally larger burst of growth factor signaling.
How PRP Is Prepared
The process starts with a standard blood draw, usually 15 to 60 mL depending on the application. That blood goes into a centrifuge, which spins it at controlled speeds to separate the components by weight. Most protocols use a two-spin method: a slower first spin separates red blood cells from plasma and platelets, then a faster second spin concentrates the platelets into a small volume of plasma. Research on optimizing this process found that specific spin speeds (160 g for 10 minutes followed by 250 g for 15 minutes) captured platelets and growth factors most efficiently while preserving platelet function.
The entire preparation takes roughly 15 to 30 minutes. Once ready, the PRP is drawn into a syringe and injected into the target area, sometimes guided by ultrasound imaging to ensure precise placement.
PRP for Joint and Tendon Injuries
Knee osteoarthritis is one of the most studied applications. A meta-analysis of clinical trials found that PRP injections produced moderate pain reduction and functional improvement compared to control groups, with an average reduction of 8.5 points on the standard WOMAC pain scale. For osteoarthritis, the optimal number of injections appears to be four, which yielded an overall response rate of about 85% in a longitudinal study. Patients with milder arthritis reached peak pain relief after the fourth injection, while those with more advanced disease needed a fifth.
For tendon injuries like rotator cuff problems, PRP’s advantage over steroid injections becomes clearer over time. In the first few weeks, steroids and PRP perform similarly for pain relief. But by 12 weeks, PRP shows significantly better functional outcomes. At 24 weeks, the gap widens further, with PRP patients scoring meaningfully higher on shoulder function assessments. This makes sense biologically: steroids reduce inflammation quickly but don’t rebuild tissue, while PRP’s repair signals take longer to produce results but create more durable improvements.
PRP for Hair Loss
For androgenetic alopecia (pattern hair loss), PRP is injected directly into the scalp at shallow depths across the thinning area. A clinical study found that hair density increased from roughly 41 hairs per square centimeter before treatment to 66 hairs per square centimeter after three monthly sessions. That’s about a 62% increase. The percentage of patients with active hair shedding (measured by a pull test) dropped from 76% to just 12% over the same period.
Sessions are typically spaced four weeks apart, with the PRP injected just a few millimeters below the skin surface using a fine needle. Each session uses about 3 to 5 mL of PRP spread across the treatment area. The growth factors stimulate dormant hair follicles, extend the active growth phase of the hair cycle, and increase blood supply to the follicle.
PRP for Skin Rejuvenation
When used for skin aging, PRP works by activating fibroblasts, the cells responsible for producing collagen and maintaining skin structure. The growth factors released from platelets bind to receptors on fibroblast surfaces, triggering them to ramp up production of collagen and other structural proteins in the skin’s deeper layers. This rebuilds the extracellular matrix that thins with age. The injection process itself also plays a small role: the micro-injuries from the needle create additional repair signals that complement the growth factor stimulation.
What Recovery Looks Like
The first few days after a PRP injection are an intentional inflammatory phase. Your body is responding to the concentrated platelets, so some increased pain, swelling, or soreness at the injection site is normal and expected. You should avoid anti-inflammatory medications like ibuprofen for two weeks after the procedure, since those drugs would counteract the very inflammation PRP is designed to trigger. Acetaminophen (Tylenol) is fine for managing discomfort.
For joint and tendon injections, plan on icing the area for 15 to 20 minutes every few hours during the first days. Strenuous activity should be avoided for two weeks, and the treated area may be immobilized with a sling or walking boot during that period. Physical therapy typically begins at the two-week mark, with a gradual return to normal activity over about six weeks. Full recovery, meaning the point where you can assess how well the treatment worked, takes three to six months. Tendon injuries generally sit at the longer end of that range.
For scalp or facial PRP, recovery is much shorter. Most people return to normal activities within a day or two, with mild redness and tenderness resolving quickly.
Who Should Not Get PRP
Because PRP concentrates growth factors that promote cell proliferation, it should not be injected near any tumor, whether benign or malignant. Patients with active cancers, cancers undergoing diagnosis, or metastatic cancers (even in remission) need oncologist clearance before considering PRP. The same caution applies to blood cancers that haven’t been stabilized.
Active infections in the treatment area are another clear contraindication. If you’re on antibiotics, PRP should wait until the course is completed. Platelet count abnormalities tied to blood disorders can also disqualify someone, though a low platelet count above 50,000 per cubic millimeter from other causes is generally not a barrier. People on blood-thinning medications or those with clotting disorders should discuss their situation with their provider, since both the blood draw and the injection carry additional considerations.