PRP vs. Cortisone Injections: An Evidence-Based Comparison

Cortisone injections have been a cornerstone of musculoskeletal pain management for decades. Platelet-rich plasma therapy has emerged as a fundamentally different approach. Both are injectable treatments delivered to the same kinds of joints and tendons, but they work through opposite biological mechanisms and produce very different outcomes over time.

This is not an argument against cortisone. It is an honest comparison of what each treatment does, what the evidence shows, and when each one is the right clinical choice. I perform both in my practice and recommend based on what the patient's tissue actually needs.

How Cortisone Works

Corticosteroid injections deliver a potent synthetic anti-inflammatory directly to the site of pain. The mechanism is straightforward: cortisone suppresses the inflammatory cascade by inhibiting prostaglandin and leukotriene synthesis, reducing vascular permeability, and blocking immune cell migration to the affected tissue. The result is rapid pain relief, often within 24 to 72 hours, and meaningful reduction in swelling.

For patients in acute pain, this is genuinely valuable. A cortisone injection into an inflamed bursa, an acutely swollen knee, or a flared tendon sheath can restore function quickly and allow the patient to participate in rehabilitation. In some cases, it also serves a diagnostic purpose: if injecting a specific structure eliminates the pain, you have confirmed the pain generator, which can guide further treatment decisions.

What cortisone does not do is repair tissue. It does not stimulate collagen synthesis, recruit reparative cells, or reverse degeneration. It suppresses the inflammatory response — which, in acute situations, is the problem. But in chronic degenerative conditions, the problem is not too much inflammation. The problem is tissue that has failed to heal. Suppressing inflammation in that context addresses the symptom while leaving the underlying pathology unchanged.

How PRP Works

Platelet-rich plasma is prepared from the patient's own blood. A venous sample is drawn, centrifuged to separate and concentrate the platelet fraction, and injected into the target tissue under ultrasound guidance. The concentrated platelets release a cascade of growth factors — platelet-derived growth factor (PDGF), transforming growth factor beta (TGF-beta), vascular endothelial growth factor (VEGF), insulin-like growth factor (IGF-1), and others — that signal the tissue to initiate active repair.

This is a fundamentally different biological proposition than cortisone. PRP does not suppress inflammation. It deliberately initiates a controlled inflammatory response — the kind the body uses to heal an acute injury. It recruits stem cells and progenitor cells to the treatment site, stimulates collagen synthesis, promotes new blood vessel formation, and shifts the tissue environment from chronic degeneration toward active regeneration.

The trade-off is time. PRP does not provide rapid pain relief. Most patients experience increased soreness for the first one to two weeks as the inflammatory healing cascade activates. Meaningful clinical improvement typically emerges at four to six weeks and continues to develop over three to six months. For a patient seeking immediate relief from an acute flare, PRP is the wrong tool. For a patient with a chronic tendon or joint problem that has failed to heal on its own, it may be exactly the right one.

Head-to-Head: What the Evidence Shows

The most instructive study in this comparison remains the work by Gosens and colleagues, published in the American Journal of Sports Medicine, examining PRP versus cortisone for lateral epicondylitis — tennis elbow. This is an ideal comparison case because lateral epicondylitis is one of the most common chronic tendinopathies, it is frequently treated with cortisone, and the tissue pathology is well characterized.

At four weeks, the cortisone group was doing better. Pain scores improved more rapidly, which is exactly what you would expect from a potent anti-inflammatory. At eight weeks, the two groups were roughly equivalent. But at one year, the PRP group had significantly better outcomes than the cortisone group. The cortisone patients had regressed — many were back to baseline or worse — while the PRP patients continued to improve.

This pattern — cortisone winning short-term, PRP winning long-term — has been replicated across multiple conditions. A 2021 meta-analysis in the British Journal of Sports Medicine found that PRP outperformed cortisone for chronic tendinopathy at follow-up periods beyond three months. For knee osteoarthritis, systematic reviews have shown PRP producing more durable pain relief and functional improvement compared to corticosteroid injection at six and twelve months.

The mechanism behind this divergence is not mysterious. Cortisone provides temporary symptom suppression without tissue repair. When the anti-inflammatory effect wears off, the underlying pathology remains. PRP stimulates actual structural change in the tissue. The improvement takes longer to manifest but reflects genuine biological repair rather than pharmacological masking.

When Cortisone Is the Right Choice

None of this means cortisone is a bad treatment. It means cortisone is a specific tool with specific appropriate uses. I still administer cortisone injections in my practice when the clinical situation calls for them.

Acute inflammatory flares. A patient with an acutely inflamed bursa, a crystal arthropathy flare (gout, pseudogout), or an acute tendon sheath inflammation needs the inflammation controlled now, not in six weeks. Cortisone is the right tool.

Diagnostic injection. When the pain generator is uncertain, injecting cortisone into a specific joint or structure under fluoroscopic or ultrasound guidance can confirm the diagnosis. If the pain resolves, you have identified the source. This information is clinically valuable regardless of the long-term treatment plan.

Bridging to rehabilitation. Some patients are in too much pain to participate in physical therapy or rehabilitation. A cortisone injection that reduces pain for four to six weeks can create a window for the patient to engage in the exercise-based treatment that will address the underlying dysfunction. In this context, cortisone is not the treatment — it is the gateway to treatment.

Patients who cannot wait. An athlete with a competition in two weeks, a patient with a critical work deadline, someone who needs functional improvement now for legitimate reasons. PRP's slower onset makes it impractical in these situations.

When PRP Is the Better Option

PRP is the stronger choice when the clinical picture involves chronic degeneration rather than acute inflammation — and when the goal is durable tissue improvement rather than temporary symptom relief.

Chronic tendinopathy. Tennis elbow, Achilles tendinopathy, patellar tendinopathy, rotator cuff tendinopathy — conditions where the tendon has undergone degenerative change (technically tendinosis, not tendinitis) and the tissue needs repair, not anti-inflammatory suppression.

Mild to moderate osteoarthritis. Cartilage degeneration in the knee, hip, or other joints where the goal is to slow progression and improve the biological environment within the joint. PRP's growth factors can modulate the intra-articular environment and support chondrocyte function in ways cortisone cannot.

Partial ligament or muscle tears. Incomplete tears where surgical intervention is not indicated but the tissue needs biological support to heal optimally.

Failed cortisone. Perhaps the clearest indication: a patient who has had two or three cortisone injections for the same problem with diminishing returns. The pattern of decreasing benefit with repeated cortisone is itself evidence that the problem is not primarily inflammatory and that a regenerative approach may be more appropriate.

The Risks of Repeated Cortisone Injections

This is where the comparison becomes most clinically important. A single cortisone injection for an appropriate indication carries minimal risk. But the pattern seen too often in practice is serial cortisone injection — three, four, five or more injections into the same joint or tendon over months or years — because the temporary relief wears off and the patient returns for another.

Repeated corticosteroid exposure has well-documented adverse effects on tissue:

• Tendon weakening and rupture. Cortisone inhibits tenocyte proliferation and collagen synthesis. Multiple injections into or near a tendon progressively weaken its structural integrity. Achilles tendon rupture following repeated cortisone injection is a recognized clinical entity.
• Cartilage thinning. Intra-articular corticosteroids accelerate cartilage degradation with repeated use. A 2017 randomized trial published in JAMA found that patients receiving triamcinolone injections every three months for two years had significantly greater cartilage volume loss compared to saline placebo — with no significant difference in pain outcomes.
• Local tissue atrophy. Subcutaneous fat atrophy and skin depigmentation at the injection site, particularly with superficial injections.
• Systemic effects. Transient blood glucose elevation (significant for diabetic patients), adrenal suppression with frequent injections, and potential effects on bone density with cumulative exposure.

The clinical guideline most physicians follow is a maximum of three to four cortisone injections per joint per year, with some experts recommending no more than three lifetime injections per tendon. When a patient has reached that threshold without lasting improvement, continuing with cortisone is not just ineffective — it is potentially harmful to the tissue you are trying to treat.

How Dr. Knopp Approaches the Decision

Every patient who comes to this practice for joint or tendon pain receives a thorough evaluation before any injection is discussed. The decision between PRP and cortisone is not ideological — it is clinical, based on what the tissue needs and what the patient's goals are.

The evaluation includes a detailed history of prior treatments (including how many cortisone injections have already been administered), a complete musculoskeletal and osteopathic structural examination, and imaging review when indicated. From that assessment, the recommendation follows the tissue, not a protocol.

For some patients, a single cortisone injection is the right first step — to reduce acute inflammation, confirm a diagnosis, or create a rehabilitation window. For others, particularly those with chronic degenerative conditions or a history of diminishing returns from cortisone, PRP offers a fundamentally different biological approach that addresses the underlying tissue pathology rather than temporarily suppressing its symptoms.

The patients I see most often for this conversation are active adults over fifty with knee or shoulder pain that has been managed with periodic cortisone for a year or more, and younger athletes with chronic tendon problems that have not responded to rest and physical therapy alone. Both groups tend to be excellent PRP candidates — and both deserve an honest discussion about what each treatment can and cannot do.