Mild to Moderate Knee Osteoarthritis

CAUSES

• Gradual breakdown of knee cartilage with age
• Prior knee injury or surgery
• Excess body weight, which increases joint loading
• Joint malalignment (bow-legged or knock-kneed)
• Genetics and family history of osteoarthritis

SYMPTOMS

• Aching knee pain that worsens with activity and improves with rest
• Morning stiffness that improves within about 30 minutes
• Grinding or crunching sensations (crepitus)
• Mild swelling after activity
• Gradually worsening range of motion

IMAGING

X-rays are the standard first step and grade the severity of arthritis. MRI is reserved for atypical cases or for suspected meniscus or cartilage problems.

CAN PRP HELP?

Knee osteoarthritis is one of the best-studied uses of PRP, and one of ASPN’s strongest-graded indications. Across many randomized trials, PRP injections outperform hyaluronic acid injections for pain and function for up to a year, particularly in younger patients with less advanced arthritis.

Leukocyte Preparation: Leukocyte-Poor

Dosing: 2-3 injection series

Target Platelet Dose in Studied Protocols: ~10 billion platelets (total platelets provided).

ASPN 2024 CONSENSUS GUIDELINE

ASPN grades this Level I, Grade B — consistent, favorable evidence. A separate 2026 AAPM&R guidance statement reaches a similar conclusion: PRP is reasonable for symptomatic Kellgren-Lawrence grade I–III knee OA, once first-line conservative care (PT, NSAIDs, activity modification) has underperformed. For grade IV, bone-on-bone disease, PRP is not recommended; total knee replacement may otherwise be considered. On leukocyte content: a series of injections (especially leukocyte-rich, in some meta-analyses) outperformed a single dose, but a 192-patient head-to-head RCT found no real difference between LR and LP at 12 months — which is why we default to the gentler leukocyte-poor preparation for this joint.

Sources: D’Souza et al. (ASPN Consensus), Journal of Pain Research, 2024 · Borg-Stein et al. (AAPM&R), PM&R, 2026 · Belk et al., American Journal of Sports Medicine, 2020 · Kim et al., Archives of Orthopaedic and Trauma Surgery, 2022

FREQUENTLY ASKED QUESTIONS

Does PRP work for knee arthritis?

Yes, for many people. Studies show PRP works better than hyaluronic acid shots for pain and movement, sometimes for up to a year. This is one of the most studied uses of PRP.

Does PRP work for severe knee arthritis?

Not as well. PRP works best for mild to moderate arthritis, once other treatments like physical therapy have not helped enough. For severe, bone-on-bone arthritis, PRP usually is not recommended, and a knee replacement may be a better option.

How many PRP injections for knee osteoarthritis?

Most plans use two to three shots. Getting a strong enough dose of platelets matters for results, and that sometimes takes more than one injection.

How does PRP compare to a hyaluronic acid shot for knee arthritis?

Across many randomized trials, PRP outperforms hyaluronic acid injections for pain and function for up to a year.

Does PRP work at every stage of knee arthritis?

It works best earlier in the arthritic process. A separate 2026 society guidance statement frames PRP as reasonable for symptomatic mild-moderate arthritis once first-line conservative care has underperformed, but is not recommended for grade IV, bone-on-bone disease.

Does the amount of PRP injected matter?

At least one randomized trial ties the outcome to the total delivered platelet count (about 10 billion platelets), which may take multiple injections to achieve.

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