PRP Injection for Knee Arthritis

PRP injection for knee arthritis uses platelet-rich plasma prepared from the patient’s blood. It may improve pain and function in selected patients, particularly with earlier arthritis, but preparation methods and results vary. PRP is not a stem-cell treatment and should not be presented as guaranteed cartilage regeneration.

Quick Answer

• PRP is a blood-derived preparation, not a stem-cell injection.

• Platelet concentration, white-cell content and final volume differ between systems.

• AAOS states that PRP may reduce pain and improve function, with a limited-strength recommendation.

• ACR strongly recommends against PRP because of heterogeneity and lack of standardisation.

• These differing positions require transparent shared decision-making rather than marketing claims.

What Is PRP?

A blood sample is centrifuged to obtain plasma with a higher platelet concentration than whole blood. Platelets release signalling proteins involved in inflammation and tissue response. The final preparation depends on the centrifugation method, platelet count, leukocyte content, activation protocol and volume.

Why PRP Products Are Not Interchangeable

Two clinics may both use the term PRP while producing biologically different preparations. Brand names alone do not prove superiority. The clinician should explain the system used, expected platelet characteristics, number of injections and why that protocol was selected.

What the Guideline Disagreement Means

AAOS considers that PRP may improve pain and function but rates the evidence as limited because studies vary substantially. ACR strongly recommends against PRP, citing heterogeneity and lack of standardisation. A guideline position does not determine an individual outcome, but it should shape honest counselling about uncertainty, cost and alternatives.

Who May Be a More Reasonable Candidate?

• Confirmed symptomatic mild or moderate knee osteoarthritis.

• Symptoms that match the involved knee compartment.

• Persistent pain despite appropriate exercise and first-line care.

• Reasonable movement without major fixed deformity or instability.

• Acceptance that benefit is variable, delayed and not guaranteed.

• Willingness to continue strengthening and weight management when relevant.

Who Is Less Likely to Benefit?

• Advanced bone-on-bone arthritis with major deformity.

• Severe stiffness, instability or constant disabling pain.

• Pain mainly from the hip, spine, tendon or another diagnosis.

• Active infection, significant anaemia or selected blood disorders.

• Expectation of guaranteed cartilage regrowth or permanent avoidance of surgery.

How PRP Is Prepared and Given

1. The diagnosis, arthritis stage and treatment goal are confirmed.

2. Medicines, supplements, infection risk and blood-related conditions are reviewed.

3. Blood is drawn and centrifuged using the selected system.

4. The platelet-rich fraction is separated.

5. The knee is cleaned using sterile technique and the preparation is injected.

6. Activity, medication, warning-sign and rehabilitation instructions are provided.

When Might It Start Working?

PRP is not usually expected to act as rapidly as corticosteroid. Some patients notice improvement over several weeks. Temporary soreness can occur. Magnitude and duration vary, so a fixed number of pain-free months should not be promised.

How Many Injections Are Needed?

Protocols include one injection or a short series. More injections are not automatically better. The plan should consider evidence for the system, total cost, arthritis stage and prior response. Automatic repetition after no meaningful benefit may be poor value.

Risks and Limitations

• Temporary pain, swelling or stiffness.

• Bruising from the blood draw or injection.

• Rare joint infection.

• No meaningful improvement.

• Variation in preparation quality and composition.

• Direct cost that may not be covered by insurance.

Medicines Before and After PRP

Instructions about anti-inflammatory medicines differ by protocol and medical condition. Patients should not stop prescribed medicine independently. Blood thinners, supplements and medicines affecting platelets or bleeding must be disclosed before the procedure.

PRP Compared With Cortisone

Corticosteroid is generally selected for faster short-term anti-inflammatory relief. PRP may have a slower onset and may provide a longer symptomatic window in some earlier-arthritis patients, but it is more expensive and less standardised. Neither is universally superior.

PRP Compared With Hyaluronic Acid

Some comparative studies favour PRP for pain or function, but results vary by preparation and patient. Hyaluronic acid and PRP have different mechanisms and guideline positions; neither restores advanced cartilage.

PRP Compared With GFC

GFC is also blood-derived but is processed to obtain a concentrated growth-factor preparation with reduced cellular content. Direct high-quality comparative evidence is limited.

Read GFC Therapy vs PRP.

Using the Treatment Window

If symptoms improve, the period should support strengthening, walking and meaningful activity. An injection without progressive rehabilitation may provide limited value.

Read Knee Arthritis Exercises.

How to Judge Whether PRP Worked

Choose a functional target before the injection: walking distance, stairs, sleep, rescue-medicine use or exercise participation. Review magnitude, duration and cost after an appropriate interval. Small day-to-day changes are not enough to justify automatic repetition.

Avoiding Regeneration Claims

Laboratory signalling effects should not be translated into a promise that a worn joint will regrow normal cartilage. PRP is best described as a possible symptom-modifying option for selected patients, with uncertain magnitude and duration of benefit.

When PRP Should Not Delay Replacement

Repeated PRP cannot correct severe deformity, major instability or advanced joint destruction. When pain substantially limits sleep, walking and independence despite appropriate care, knee replacement should be discussed honestly.

Read When Does Knee Arthritis Need Replacement?.

Questions Patients Commonly Ask

Is PRP a stem-cell injection?

No. PRP is platelet-rich plasma prepared from blood.

Does PRP regrow knee cartilage?

It has not been proven to restore advanced cartilage loss to a normal joint. Guaranteed regeneration claims are misleading.

How long does PRP last?

Benefit, when present, may last for months, but there is no guaranteed duration.

Is PRP useful in bone-on-bone arthritis?

The chance of meaningful benefit is generally lower in advanced disease, and replacement may be more predictable.

Why do guidelines disagree?

They weigh heterogeneous preparations, study quality, average benefit, cost and recommendation thresholds differently.

Warning Signs After Injection

Severe pain, fever, a hot red knee, rapidly increasing swelling or inability to bear weight requires urgent assessment rather than waiting for routine follow-up.

Clinical References

AAOS Clinical Practice Guideline: Management of Osteoarthritis of the Knee (Non-Arthroplasty)

American College of Rheumatology Osteoarthritis Guideline

NICE NG226: Osteoarthritis in over 16s—diagnosis and management

About Dr. Mayur Rabhadiya

Dr. Mayur Rabhadiya is an Orthopedic and Joint Replacement Surgeon in Mumbai. Qualifications: MBBS, D’Ortho, DNB (Orthopedics), MNAMS (Orthopedics), FIJR (Robotic & Navigation). Read his professional profile.

Book a Consultation

Consultations are available in Ghatkopar East and Ghatkopar West, Mumbai. Call or WhatsApp +91 84249 03913 or +91 96113 30063, or use the appointment page.

Medical Author and Reviewer

Written and medically reviewed by Dr. Mayur Rabhadiya, MBBS, D’Ortho, DNB (Orthopedics), MNAMS (Orthopedics), FIJR (Robotic & Navigation). Last medically reviewed: 17 July 2026.

Medical Disclaimer

This guide provides general education and does not replace individual examination, injection consent or treatment advice.