PRP vs. Cortisone for Knee Pain: What Does the Evidence Actually Show?

For medical review by the Hip & Knee and Sports Medicine Teams at Lancaster Orthopedic Group.

When knee arthritis makes walking, stairs, exercise, or sleep uncomfortable, injections can sound like a straightforward next step. The choice is often presented as cortisone for quick relief or platelet-rich plasma, commonly called PRP, for a more biologic approach.

That summary is directionally useful, but incomplete. Cortisone and PRP work differently, the quality of evidence is not the same, and neither injection is appropriate for every kind of knee pain. The best choice depends on the diagnosis, how quickly relief is needed, how long symptoms have lasted, the severity of arthritis, medical history, cost, and what you plan to do with the improvement.

First, Make Sure the Pain Is Actually Knee Osteoarthritis

Most research comparing PRP and cortisone focuses on symptomatic knee osteoarthritis. That is different from a recent meniscus tear, ligament injury, fracture, infection, gout flare, inflammatory arthritis, or pain referred from the hip or spine.

An injection should follow a diagnosis. The history, examination, and usually weight-bearing X-rays help determine whether arthritis matches the location and pattern of pain. If the knee is suddenly very swollen, hot, red, or impossible to bear weight on, the priority is ruling out an urgent condition rather than choosing an elective injection.

What a Cortisone Injection Does

Cortisone is a corticosteroid medication that reduces inflammation inside the joint. It does not replace cartilage or reverse arthritis. Its practical value is speed: many patients who respond notice improvement within several days.

The American Academy of Orthopaedic Surgeons gives intra-articular corticosteroids a moderate recommendation for short-term relief in symptomatic knee osteoarthritis. In the evidence reviewed for that guideline, improvement in pain and function generally lasted no longer than about three months.

• Potential advantage: faster, more predictable short-term anti-inflammatory relief.
• Potential advantage: commonly available and more likely to be covered by insurance.
• Limitation: benefit may fade within weeks or a few months.
• Limitation: repeated injections require thoughtful timing because cumulative use may affect joint tissues and future treatment planning.

Blood sugar may rise temporarily after a steroid injection, particularly in people with diabetes. A short-lived pain flare can occur, and infection is rare but serious. The treating clinician should review medical conditions, medications, prior injections, and any planned surgery.

What PRP Is - and What It Is Not

PRP is prepared from a sample of your own blood. The blood is processed to concentrate platelets and other components, and the resulting product is injected into the knee. Platelets release signaling proteins that may influence inflammation and tissue response.

PRP is not a steroid, a stem-cell treatment, or a proven way to regrow a worn-out knee. It is also not one standardized product. Platelet concentration, white-cell content, activation method, injection volume, and number of injections vary across clinics and studies. That variability is one reason the evidence is difficult to interpret.

• Potential advantage: some studies show longer improvement in pain and function than cortisone.
• Potential advantage: it uses an autologous product prepared from the patient’s own blood.
• Limitation: results are less predictable and relief usually is not immediate.
• Limitation: cost and insurance coverage can be significant barriers.

What the Evidence Actually Shows

The most honest conclusion is that the evidence favors different strengths for each treatment. Cortisone has clearer support for short-term symptom relief. PRP has a growing body of studies suggesting that some patients experience better pain and function outcomes later in follow-up, often around three to twelve months.

Recent systematic reviews comparing PRP with corticosteroid injections generally find little or no meaningful difference very early, followed by an advantage for PRP at later follow-up. However, results vary by study, and not every statistical difference is large enough for patients to feel as a meaningful change.

The AAOS guideline reflects that uncertainty. It says PRP may reduce pain and improve function in symptomatic knee osteoarthritis, but labels the recommendation “limited” because the evidence is inconsistent. That is not the same as saying PRP does not work. It means clinicians should be careful about promising who will respond, how much improvement to expect, and which preparation is best.

Why the Studies Do Not Produce One Simple Winner

PRP preparations are not standardized

Two treatments both labeled PRP may contain different platelet doses, white-cell levels, and total volumes. Some protocols use one injection while others use two or three. Pooling those studies can hide important differences.

Knee arthritis is not one uniform condition

A patient with mild compartment arthritis, good alignment, and an active lifestyle is not the same as a patient with severe bone-on-bone narrowing, major deformity, and pain at rest. Response rates can change with arthritis severity, age, weight, inflammation, and other health factors.

Comparison groups and follow-up periods vary

A study that measures pain at four weeks may favor the faster treatment. A study that measures function at six or twelve months may produce a different result. Placebo response is also substantial with injections, making well-designed blinded trials especially important.

Pain relief is not cartilage restoration

An improvement in pain or function does not prove that cartilage grew back or arthritis reversed. Imaging studies have not established PRP as a dependable disease-modifying treatment. The realistic goal is symptom improvement and better function.

A Practical Head-to-Head Comparison

Which tends to work faster?

Cortisone. When it helps, relief often begins within days. PRP may cause temporary soreness first, and improvement can take several weeks.

Which may last longer?

PRP may provide longer benefit for some patients with knee osteoarthritis, particularly when compared at six months or later. The duration is variable, and neither treatment guarantees a specific number of pain-free months.

Which has the stronger guideline recommendation?

For knee osteoarthritis, AAOS gives corticosteroid injections a moderate recommendation for short-term relief and PRP a limited recommendation for possible pain and function improvement.

Which is less expensive?

Cortisone is generally less expensive and more commonly covered. PRP is often paid out of pocket. Patients should confirm the complete cost, including whether the quoted price covers one injection or a series.

Which is safer?

Both are generally performed as office-based injections, but both have risks. Infection, bleeding, pain flare, and failure to improve are possible. Cortisone has medication-specific considerations such as blood-sugar elevation and concerns with frequent repetition. PRP commonly causes short-term soreness and may be unsuitable when certain blood, infection, or medication issues are present.

Who Might Consider Cortisone First?

• A patient who needs faster short-term relief to sleep, travel, or participate in rehabilitation.
• A patient with an inflammatory flare or significant joint swelling that fits the diagnosis.
• A patient for whom cost or insurance coverage makes PRP impractical.
• A patient who understands that the benefit may be temporary and is using the relief to strengthen, lose weight, or regain activity.

Who Might Discuss PRP?

• A patient with mild to medium symptomatic knee osteoarthritis who has not improved enough with exercise, medication, or other conservative care. If the osteoarthritis is severe, a PRP injection may not be beneficial.
• A patient who accepts a slower onset and uncertain response in exchange for the possibility of longer symptom improvement.
• A patient who can manage the out-of-pocket cost and understands that protocols vary.
• A patient whose arthritis severity, alignment, health, and treatment goals make PRP a reasonable option after examination.

These are discussion points, not eligibility rules. A clinician still needs to confirm the diagnosis and review contraindications.

Neither Injection Replaces the Rest of the Treatment Plan

An injection is most useful when it creates an opportunity to do something that improves long-term function. That may mean participating in physical therapy, rebuilding quadriceps and hip strength, gradually increasing walking, reducing excess load on the joint, or returning to a manageable exercise routine.

If the knee remains severely limiting despite appropriate non-surgical care, repeated injections should not become a substitute for reassessing the diagnosis or discussing surgical options. Advanced arthritis with major deformity or constant pain may respond differently than earlier disease.

Questions to Ask Before Choosing an Injection

• What diagnosis are we treating, and does my examination match knee osteoarthritis?
• How severe is the arthritis, and how does that affect the chance of improvement?
• What result should I expect at one month, three months, and six months?
• If this is PRP, what preparation and number of injections do you use, and why?
• What is the total cost, and what does insurance cover?
• How will we use any pain relief to improve strength and function?
• At what point should we stop repeating injections and reconsider the overall plan?

Planning Knee Arthritis Care in Lancaster County

Lancaster Orthopedic Group’s hip and knee and sports medicine teams evaluate both surgical and non-surgical causes of knee pain. Imaging, rehabilitation, injections, and surgical consultation can be coordinated around the diagnosis and the activities a patient wants to regain.

The decision between PRP and cortisone should not begin with which injection sounds newer. It should begin with what is causing the pain, what outcome matters most, and how the injection fits into the next phase of care.

Frequently Asked Questions

Does PRP regrow knee cartilage?

Current evidence does not support promising that PRP reliably regrows lost cartilage or reverses osteoarthritis. The demonstrated outcome is symptom improvement in some patients, not restoration of a normal joint.

How many PRP injections are needed?

Protocols vary from one injection to a series. Research has not established one best schedule for every patient. Ask which protocol is being recommended, what evidence supports it, and whether the quoted cost covers the full plan.

How often can cortisone shots be repeated?

There is no universal schedule that is right for every knee. Frequency depends on the diagnosis, response, medical history, previous injections, and future surgical plans. Repeating an injection that provides little or very brief relief should trigger reassessment.

Will insurance cover PRP?

Coverage varies and PRP for knee osteoarthritis is often considered an out-of-pocket treatment. Confirm benefits and the clinic’s complete pricing before scheduling.

Can an injection help me avoid knee replacement?

An injection may delay surgery by improving symptoms and function, but it cannot guarantee that replacement will never be needed. The decision depends on pain, disability, arthritis severity, overall health, and response to non-surgical care.

Wrapping Up

Cortisone and PRP are not interchangeable, and the evidence does not crown one winner for every patient. Cortisone is supported for faster, short-term relief. PRP may offer longer improvement for some people, but the evidence is less consistent because the treatment and study populations vary.

The right choice begins with a confirmed diagnosis, realistic expectations, and a plan for what happens after the injection. Relief matters most when it helps you move, strengthen, and return to the activities the knee has interrupted.

Call 717-560-4200 or request an appointment online to get started.