What is PRP Therapy and How Does It Work?

Platelet-rich plasma therapy uses your own blood to stimulate tissue repair. A plain-language explanation of how it is made, what it does, and which conditions have the strongest evidence.

Platelet-rich plasma (PRP) therapy has become one of the most widely discussed treatments in musculoskeletal medicine. It is used for knee osteoarthritis, tendon injuries, joint pain, and a range of other conditions — but it is often described in vague or overly technical terms. This post explains what PRP actually is, how it is prepared and administered, what it does biologically, and which conditions have the strongest supporting evidence.

What is PRP?

PRP stands for platelet-rich plasma. It is prepared from a patient's own blood — no donor blood, no synthetic materials. A standard blood draw is taken and placed into a centrifuge, which spins the blood at high speed to separate its components. Red blood cells fall to the bottom. Plasma rises to the top. Platelets concentrate in a layer between them.

The platelet-rich layer is extracted and, depending on the preparation, may be further concentrated or mixed with a small amount of plasma. The result is a fluid with a platelet concentration several times higher than normal blood, which is then injected into the affected tissue using ultrasound guidance to confirm accurate placement.

What do platelets do?

Platelets are best known for their role in clotting — stopping bleeding after an injury. But they do considerably more than that. Platelets are storage vehicles for a large library of growth factors and signaling proteins that play a direct role in tissue repair.

When platelets are activated at an injury site, they release these growth factors into the surrounding tissue. These proteins signal the body to recruit repair cells, stimulate collagen production, promote new blood vessel formation, and regulate the local healing environment. In plain terms, they trigger and sustain the repair process.

In healthy tissue that has been acutely injured, the body does this naturally. The problem with chronic tendon degeneration and joint osteoarthritis is that this repair signaling has broken down or become insufficient. The tissue has shifted from an active healing state to a chronic degenerative state. PRP is an attempt to restart that repair response by delivering a concentrated dose of the signals that drive it.

How is it different from cortisone?

This is the most common comparison patients ask about. Cortisone (corticosteroid) injections suppress inflammation. They work quickly and can provide meaningful short-term relief. PRP does something different: rather than suppressing the inflammatory response, it attempts to direct tissue toward active repair.

For acute inflammatory conditions — a flare of bursitis, for example — cortisone can be appropriate. For chronic degenerative conditions like knee osteoarthritis or tendinopathy, where the problem is structural breakdown rather than acute inflammation, the evidence increasingly favors PRP for durable long-term improvement.

What conditions does PRP treat?

PRP has been studied extensively across a range of musculoskeletal conditions. The conditions with the strongest randomized trial support include:

• Knee osteoarthritis — the most studied application, with multiple meta-analyses showing PRP superior to corticosteroid and hyaluronic acid at 6 and 12 months
• Tennis elbow (lateral epicondylitis) — consistent RCT evidence showing PRP outperforms corticosteroid at 3, 6, and 12 months
• Plantar fasciitis — strong trial support, both as a standalone injection and combined with shockwave therapy
• Patellar tendinopathy — moderate-to-strong evidence, particularly when combined with a structured loading program
• Rotator cuff tendinopathy — favorable results in several trials for chronic tendinopathy specifically
• Frozen shoulder (adhesive capsulitis) — PRP outperforms corticosteroid at 3 and 6 months in a 2025 meta-analysis of 7 RCTs

What does the procedure involve?

The process takes approximately 45–60 minutes from start to finish. A blood draw is performed — typically 15–30 ml depending on the preparation used. The blood is processed in a centrifuge for 8–15 minutes. The platelet-rich layer is extracted and the injection is prepared.

The injection itself is performed under ultrasound guidance. Real-time imaging allows the clinician to confirm the needle is positioned accurately within the target tissue — whether that is a joint space, a tendon insertion, or a fascial attachment. This matters because accurate placement significantly affects outcomes.

After the injection, mild soreness at the injection site is common for 2–5 days. This is a normal part of the healing response. Most protocols involve a short period of relative rest followed by a graduated return to activity or a structured rehabilitation program, depending on the condition.

How many injections are needed?

This varies by condition and by the individual's response. For knee osteoarthritis, most protocols use one to three injections, often spaced several weeks apart. For tendon conditions, a single injection combined with a loading program is frequently the starting point. Some patients respond well to a single injection; others benefit from a series.

The right number is determined by your response to treatment and the evidence for your specific condition — a conversation worth having at your initial visit.

The bottom line

PRP therapy uses a concentration of your own platelets to deliver growth factor signals directly into damaged tissue, with the goal of stimulating repair rather than suppressing symptoms. For knee osteoarthritis, tennis elbow, plantar fasciitis, frozen shoulder, and several other conditions, it has a meaningful and growing evidence base — and for many patients, results that cortisone alone cannot match over the long term.