Knee osteoarthritis is one of the most common reasons patients come to Purety Family Medical Clinic seeking an alternative to conventional care. Most have already tried cortisone shots — some multiple times — and are frustrated with diminishing returns. Many are trying to avoid, or at least delay, knee replacement surgery. PRP (Platelet-Rich Plasma) is increasingly well-supported by evidence as a meaningful option. Here's a plain-English review of what the research actually shows.
What Is Knee Osteoarthritis?
Knee osteoarthritis (OA) is the progressive loss of articular cartilage in the knee joint — the smooth tissue that allows bones to glide over each other without friction. As cartilage wears away, bone-on-bone contact increases, causing pain, stiffness, swelling, and reduced range of motion. It's the leading cause of disability in adults over 50 and affects an estimated 32.5 million Americans.
Standard treatment follows a predictable escalation: NSAIDs, then physical therapy, then cortisone or hyaluronic acid injections, then eventually knee replacement surgery. Each step manages symptoms but none of the conventional options — including surgery — actually restore cartilage. They buy time. PRP is the only widely available injectable treatment with a plausible mechanism for actually slowing the degenerative process.
What Does PRP Do in an Arthritic Knee?
PRP is concentrated from a sample of your own blood. The platelet-rich fraction is separated by centrifuge and injected into the knee joint under ultrasound guidance. Platelets release a cascade of growth factors — including PDGF, TGF-β, IGF-1, and FGF — that are directly involved in cartilage metabolism and repair.
In the context of knee OA, PRP has several documented effects: it promotes chondrocyte proliferation (the cells that maintain cartilage), reduces inflammatory cytokines like IL-1β and TNF-α that drive cartilage degradation, and stimulates production of synovial fluid — the natural lubricant of the joint. These mechanisms address some of the root drivers of OA progression rather than simply masking pain.
What the Research Shows
The evidence base for PRP in knee OA has grown substantially. Here are some of the most important findings:
PRP vs. Hyaluronic Acid
A 2022 systematic review and meta-analysis published in the Journal of Orthopaedic Surgery and Research, which analyzed 25 randomized controlled trials with over 2,000 patients, found that PRP produced significantly better pain reduction and functional improvement compared to hyaluronic acid at 6 and 12 months. The advantage was most pronounced in patients with mild-to-moderate OA (Kellgren-Lawrence grades 1–3).
PRP vs. Cortisone
Multiple head-to-head trials have now compared PRP directly to corticosteroid injections. While cortisone consistently outperforms PRP at 4–6 weeks (the short-term advantage of anti-inflammatory suppression), PRP shows superior outcomes at 3, 6, and 12 months. A 2021 RCT in the American Journal of Sports Medicine found that PRP patients had 40% greater reduction in KOOS (Knee Injury and Osteoarthritis Outcome Score) pain subscores at 12 months compared to cortisone. The cortisone group showed measurable decline in function at 12 months — consistent with the known tissue effects of repeated corticosteroid exposure.
Long-Term Cartilage Effects
A 2020 study using MRI cartilage mapping found that patients receiving PRP had significantly less cartilage volume loss at 12 months compared to patients receiving saline control injections. This is a meaningful finding: PRP appears to slow the degenerative process, not just reduce symptoms. No conventional injection therapy — including cortisone and hyaluronic acid — has demonstrated this effect.
Who Is a Good Candidate for PRP?
PRP is best supported in patients with mild-to-moderate knee OA (Kellgren-Lawrence grades 1–3). Evidence is more limited for severe, bone-on-bone OA (grade 4), where the structural damage is extensive and the remaining cartilage too compromised to benefit meaningfully from growth factor stimulation.
Good candidates typically include:
- Patients with persistent knee pain despite NSAIDs and physical therapy
- Those who have had cortisone injections with diminishing returns
- Younger patients (under 65) trying to delay or avoid knee replacement
- Active patients with moderate OA who want to maintain function and sport
- Patients with hyaluronic acid treatment history who want a more regenerative option
Patients who are not good candidates include those with severe grade 4 OA, active infection, bleeding disorders, or certain autoimmune conditions affecting the knee. A thorough evaluation — including musculoskeletal ultrasound — helps confirm candidacy.
Why Ultrasound Guidance Matters for Knee PRP
The knee may seem like an easy target for injection — it's a large joint. But studies show that unguided injections miss the intra-articular space in 20–30% of cases, even in experienced hands. Inaccurate placement means the growth factors in your PRP never reach their target.
Dr. Birch is certified in musculoskeletal sonography (RMSK) — a credential held by very few naturopathic or integrative physicians. Every PRP injection at Purety Clinic is performed under real-time ultrasound guidance, with visual confirmation of needle placement inside the joint. This precision is not a luxury — it's a basic standard of care that directly affects outcomes.
What to Expect: Protocol and Recovery
Most patients with knee OA receive 1–3 PRP injections spaced 4–6 weeks apart, depending on severity and response. The procedure takes about 45–60 minutes including preparation and processing. There may be mild soreness in the first 48–72 hours as the inflammatory healing response is activated. Most patients can walk immediately afterward, though high-impact activity is typically restricted for 1–2 weeks.
Meaningful improvement is usually noticed between 4–8 weeks and continues over 3–6 months. Some patients experience durable benefit for 12–18 months or longer before considering retreatment.
To schedule a PRP consultation or learn more about regenerative injections at Purety Clinic, call (805) 500-8300. We also work with patients with a range of orthopedic injuries and offer a full menu of regenerative medicine services including stem cell matrix, prolotherapy, and prolozone.
