PRP Injections

PRP is derived entirely from the patient’s own blood. A small sample is drawn and placed in a centrifuge, where it is spun at controlled speeds until the different blood components separate by density. Red blood cells, being the heaviest, settle at the bottom; plasma rises to the top; and the platelets and white blood cells stratify in between. The centrifugation process takes approximately 12 minutes and yields a platelet concentration roughly three to five times higher than what is naturally present in the bloodstream.

Because red blood cells are harmful when injected into a joint, they are excluded from the final preparation. Recent research has also highlighted that elevated white blood cell content can promote, rather than reduce, inflammation within the joint. For this reason, a preparation that isolates platelets and plasma, sometimes called leukocyte-poor, or low white blood cell, PRP, is considered the most beneficial formulation for joint treatment. Just before injection, a platelet activator may be added to begin the clotting cascade and produce a platelet gel.

Multiple clinical trials have demonstrated that leukocyte-poor PRP outperforms placebo, corticosteroid injections, and hyaluronic acid gel injections for the treatment of mild to moderate knee osteoarthritis symptoms. As with other biologic therapies, earlier-stage disease tends to respond better than advanced arthritis. When compared directly with corticosteroid injections in patients with advanced knee osteoarthritis, PRP has generally shown a greater magnitude of improvement.

For patients with early osteoarthritis, a minimum of two injections has been shown to produce better outcomes than a single treatment. In patients with advanced disease, additional injections beyond the initial series have not consistently improved results. European researchers have suggested the average duration of symptom relief following a PRP injection is approximately nine months and that annual injections may help sustain the benefit. It is important to note, however, that although PRP reliably improves symptoms, no study to date has demonstrated actual cartilage regeneration.

There is growing evidence that combining PRP with a hyaluronic acid (HA) gel injection may produce a more powerful therapeutic effect than either treatment alone. The two substances may work synergistically to amplify the body’s healing response and more effectively suppress joint inflammation. A clinical trial directly comparing PRP alone, HA alone, and the combination found that patients who received both experienced significantly greater pain reduction and improved physical function compared with those who received either treatment in isolation, with the advantages measurable at one and three months and sustained through one year of follow-up.

The adverse effects associated with PRP injections are largely consistent with those seen with any intra-articular biologic injection. They include temporary pain, stiffness, dizziness, headache, nausea, sweating, and an elevated heart rate, most of which resolve within a few days. As with all injections that enter a joint, there is a small risk of infection. PRP preparations with higher white blood cell content carry a greater risk of provoking an inflammatory reaction within the joint.