Specialty
Adjunctive options — not a primary therapy and not a substitute for evidence-based surgical or non-surgical care. Honest, evidence-graded evaluation of PRP, hyaluronic acid, BMAC, Lipogems, cortisone, and "stem cell" claims, with Dr. Sabrina Strickland at the Hospital for Special Surgery in New York.
PRP and other biologic injections are adjunctive, not primary, treatments for the knee. The strongest evidence for PRP at the knee is chronic patellar tendinopathy ("jumper's knee") that has failed structured PT. The evidence for PRP in mild knee osteoarthritis is mixed — some patients respond, some do not, and no biologic injection has been shown to regenerate cartilage. PRP is FDA-permitted as a blood derivative; BMAC and Lipogems are FDA-cleared for autologous use; often "stem cell" therapy as marketed by many cash-pay clinics is not FDA-approved for orthopedic use, and claims of cartilage regeneration in adult arthritic knees are not supported by current evidence. Dr. Sabrina Strickland may discuss biologic injections within a comprehensive treatment plan in selected patients — alongside structured PT, weight optimization, hyaluronic acid where appropriate, joint-preserving surgery (osteotomy, the MISHA implantable shock absorber), cartilage restoration (MACI, OATS, allograft), or partial / total knee replacement (Mako robotic-assisted) when indicated. Biologics do not replace any of these.
This page is intentionally cautious. The orthobiologic space attracts marketing that runs ahead of the evidence, and many patients arrive at consultation having paid thousands of dollars to a clinic for "stem cell" injections that promised arthritis cure or cartilage regrowth. Neither outcome is supported by the evidence. The honest position is more limited but still useful: well-selected patients with chronic patellar tendinopathy or mild to moderate knee osteoarthritis can sometimes get meaningful symptom relief from PRP as an adjunct to structured PT and weight optimization. That is the realistic ceiling. PRP does not regrow cartilage, does not reverse advanced arthritis, and does not replace surgery when surgery is indicated.
This page covers the honest framing of biologic injections, the FDA and regulatory landscape, the five main injection options (PRP, hyaluronic acid, cortisone, BMAC, Lipogems) with evidence grades and cost, PRP in detail by indication, who is and is not a candidate, the role of biologics within a comprehensive joint-preservation strategy, what to be skeptical of when evaluating cash-pay clinic claims, what to expect on injection day, recovery, risks, common patient concerns, insurance and cost, when to seek a sub-specialty second opinion, and where Dr. Strickland sees patients. For closely related conditions and procedures, see knee arthritis for the full arthritis treatment ladder, anterior knee pain for chronic patellar tendinopathy and chondromalacia, MACI cartilage repair for the actual evidence-based option for focal cartilage damage, joint preservation and osteotomy for alignment correction, sports injuries, and ACL tear surgery for context on PRP as a research-stage adjunct in ACL healing.
Orthobiologic injections are one of the most marketed and least understood areas of orthopedic medicine. Patients arrive at consultations having read claims that PRP "regrows cartilage," that stem cells "reverse arthritis," and that biologic injections can replace joint replacement surgery. The honest reality is more limited but still useful:
Setting realistic expectations is the foundation of honest biologic injection care. Patients who arrive expecting cartilage regeneration leave disappointed even when they get meaningful symptom relief. Patients who arrive understanding that PRP is an adjunct — one tool among many — can make a clear-eyed decision about whether the cost and the realistic benefit are worth it for their situation.
The regulatory status of biologic injections is more complicated than many marketing pages suggest. Three categories matter:
PRP prepared from the patient's own blood, processed at the bedside, and re-injected on the same day is regulated as a "minimally manipulated, autologous, same-surgical-procedure" tissue. It is permitted under existing FDA frameworks and does not require a new FDA approval for each clinical use. PRP centrifuge systems used to prepare the platelet concentrate are FDA-cleared as devices. PRP is not FDA-approved as a drug for any specific orthopedic indication — which is why insurance generally classifies it as investigational.
The systems used to harvest, process, and re-inject the patient's own bone marrow (BMAC) or adipose tissue (Lipogems) are FDA-cleared as devices for that intended use. The biologic product itself is the patient's own tissue, processed minimally and re-injected the same day. Like PRP, BMAC and Lipogems are not FDA-approved as drugs for specific orthopedic indications.
Stem cell therapy as marketed by many cash-pay clinics — particularly amniotic-derived, umbilical-cord-derived, or "live cell" products — is not FDA-approved for orthopedic use. The FDA has issued warnings about specific products and clinics, and several products have been the subject of enforcement action. Independent analyses have shown that many of these products contain few if any viable stem cells after processing, and clinical claims of cartilage regeneration are not supported by the evidence.
Patients should be skeptical of any clinic — particularly cash-pay clinics not led by board-certified orthopedic surgeons — that promises knee arthritis cure, cartilage regrowth, or that "stem cells" can replace surgery. The marketing language is often deliberately vague about what is and is not in the syringe. If a clinic cannot tell you exactly what tissue type is being injected, where it came from, how it was processed, and what the published evidence is for that specific indication, that is information.
Legitimate biologic care uses your own tissue (PRP from your blood, BMAC from your bone marrow, Lipogems from your fat), frames the role honestly as adjunctive, sits inside a comprehensive treatment plan led by a board-certified orthopedic surgeon, and is direct about the possibility of non-response.
Five injections are commonly discussed for the knee, with very different evidence bases, regulatory status, and cost. The table below is the honest summary:
| Injection | What it is | Evidence at the knee | Insurance |
|---|---|---|---|
| Cortisone | Steroid anti-inflammatory | Strong for short-term flare control; repeated use associated with cartilage thinning in some studies | Covered |
| Hyaluronic acid | Joint-lubricant supplement (Synvisc, Euflexxa, Orthovisc, Monovisc, others) | Modest benefit in mild to moderate OA in responders; about half of patients respond meaningfully, half do not | Generally covered with prior auth for documented OA |
| PRP | Concentrated platelets from your own blood; growth-factor delivery | Strongest for chronic patellar tendinopathy after failed PT; mixed for mild knee OA; research-stage adjunct in ACL healing | Generally not covered; out-of-pocket |
| BMAC | Bone marrow drawn from iliac crest, processed, injected; stem-cell-rich fraction | Less mature evidence base than PRP; selected joint-preservation candidates | Generally not covered; out-of-pocket |
| Lipogems | Small autologous fat sample, processed at the bedside, injected; cellular and structural fat | Newer; evidence still developing; reasonable to consider in selected patients | Generally not covered; out-of-pocket |
Two important caveats: none of these regenerates cartilage, and amniotic / umbilical "stem cell" products marketed by some clinics are a separate category — not FDA-approved for orthopedic use, with claims unsupported by current evidence and FDA warnings on file. Those products are discussed in "What to be skeptical of" below.
Platelet-rich plasma (PRP) is prepared by drawing the patient's blood, centrifuging to separate the platelet-rich fraction from red blood cells and plasma, and injecting the concentrated platelet fraction (often under ultrasound guidance) into the affected joint or tendon. Platelets release growth factors that aim to modulate the joint or tendon environment over weeks to months. Different PRP preparations differ in their leukocyte (white-cell) content — leukocyte-rich PRP (LR-PRP) is generally favored for tendon work; leukocyte-poor PRP (LP-PRP) is generally favored for intra-articular use in osteoarthritis. Preparation systems vary in platelet concentration, and that variation is one reason clinical-trial outcomes have been heterogeneous.
All PRP products are not the same. The type of centrifuge and type of prep system vary, and that variation affects the quality of the PRP.
The best-evidenced knee indication for PRP is chronic patellar tendinopathy ("jumper's knee") — degenerative tendon pain at the inferior pole of the patella that has failed at least 3 to 6 months of structured eccentric loading rehabilitation. Multiple randomized trials and systematic reviews show that LR-PRP injections can produce meaningful symptom improvement in this population over months. PRP for refractory patellar tendinopathy after failed PT is a reasonable adjunct with reasonable evidence. For more on patellar tendinopathy and anterior knee pain, see anterior knee pain.
PRP for mild to moderate knee OA has been studied in many trials, with heterogeneous protocols and heterogeneous outcomes. The honest summary: some patients respond meaningfully, some do not, and the magnitude of benefit in responders is modest. Where PRP is used for OA, it is best understood as an adjunct that may delay further intervention in selected patients with mild to moderate disease, well-preserved alignment, no major mechanical symptoms, and realistic expectations. It is not a substitute for structured PT, weight optimization, or evidence-based surgical care when surgical care is indicated.
PRP has been studied as an adjunct to ACL surgery and as a potential aid to native ACL healing. The evidence is still developing, and PRP for ACL healing or ACL-graft maturation is not standard of care. For the patient-facing summary of one such study, see Dr. Strickland's discussion of the orthobiologics study on ACLs and platelet-rich plasma. For the surgical procedure itself, see ACL tear surgery.
Hyaluronic acid (HA) is a major component of normal synovial fluid and contributes to joint lubrication and shock absorption. HA injections (viscosupplementation) supplement the natural HA in the joint with a higher-molecular-weight or cross-linked product that lasts longer than the body's own. HA is FDA-approved for symptomatic knee osteoarthritis, which is why it sits in a different regulatory and insurance category than PRP.
BMAC (bone marrow aspirate concentrate) and Lipogems are the two main "cellular" autologous orthobiologic options. Both use the patient's own tissue — bone marrow from the iliac crest in BMAC, fat from a small liposuction sample in Lipogems — processed at the time of injection and delivered into the affected joint.
Both contain a fraction of cells that include mesenchymal stromal cells (sometimes loosely called "stem cells," though the more accurate term is mesenchymal stromal cells), as well as growth factors, cytokines, and structural elements. The cellular content and active biological role of these injections is still being characterized in research. The evidence base is less mature than for PRP and HA.
For Dr. Strickland's broader commentary on stem cells, exosomes, and what is and is not realistic for cartilage repair, see stem cells, exosomes & cartilage repair.
Cortisone (corticosteroid) injections are the oldest and most established knee injection. Cortisone is a powerful anti-inflammatory steroid that reduces joint inflammation and provides short-term symptom relief.
Repeated cortisone injections in arthritic joints have been associated with cartilage thinning in some published studies. Cortisone is best used selectively rather than as an indefinite "every three months" routine. For joint-preservation candidates earlier in the disease course, hyaluronic acid, PRP, structured PT, weight optimization, or — when imaging supports it — joint-preserving surgery may be more appropriate than repeated cortisone.
The biggest predictor of biologic injection success is patient selection. Indication-by-indication:
Biologic injections work best as one element of a broader plan, not as a stand-alone solution. A comprehensive joint-preservation plan for a patient with mild to moderate knee osteoarthritis might include:
Biologic injections fit into this continuum — they may extend the joint-preservation phase of care for selected patients, and they are rarely the entire plan. The other items on this list are not optional; biologics on top of "did nothing else" almost never produce a satisfying outcome. The other items without biologics, on the other hand, can produce a great outcome in many patients.
The orthobiologic space attracts marketing that runs ahead of the evidence, particularly from cash-pay clinics not led by board-certified orthopedic surgeons. Specific claims to be skeptical of:
Patients should be skeptical of any clinic — particularly cash-pay clinics not led by board-certified orthopedic surgeons — that promises knee arthritis cure, cartilage regrowth, or that “stem cells” can replace surgery. The marketing language is often deliberately vague about what is and is not in the syringe. If a clinic cannot tell you exactly what tissue type is being injected, where it came from, how it was processed, and what the published evidence is for that specific indication, then one should be skeptical.
If a clinic's marketing language sounds substantially different from what your orthopedic surgeon describes, that gap is information — not necessarily that the surgeon is wrong, but that the marketing is operating in a different evidence framework. Most clinics with bold "stem cell" claims for knee arthritis are predatory; a sub-specialty second opinion with a board-certified orthopedic surgeon costs less than a single injection and is much more likely to give you an accurate picture of your options.
Whether or not biologic injection is part of the plan, structured non-surgical care comes first. Patients who have skipped PT and arrive asking for "the stem cell shot" are almost always better served by a course of evidence-based foundational care before any biologic decision:
This is not delaying your care — this is your care. Biologic injections layered onto a foundation of structured PT and weight optimization have a chance of producing meaningful benefit. Biologic injections layered onto "did nothing else" usually do not.
The injection itself is an office-based procedure, typically 30 minutes total from check-in to check-out for PRP, HA, or cortisone; longer for BMAC (which requires bone marrow aspiration) or Lipogems (which requires a small lipoaspirate). The general experience:
Most patients experience mild soreness for 1 to 3 days after the injection — the platelet or marrow product itself can produce a transient inflammatory response, particularly with PRP. If clinical benefit is going to occur, it typically becomes apparent at 4 to 12 weeks, not the next day.
| Item | Typical timeline | Notes |
|---|---|---|
| Return to walking / desk work | Same day | Mild soreness expected; ice and rest the day of |
| Mild post-injection soreness | 1 to 3 days | Particularly with PRP; transient inflammatory flare is normal |
| Avoid NSAIDs (PRP only) | ~1 week before and after | NSAIDs may blunt the platelet biology; cleared individually |
| Resume structured PT | 3 to 7 days | Continue eccentric loading or OA-appropriate program |
| Earliest clinical response (if any) | 4 to 6 weeks | Reassess at the 4 to 6 week visit |
| Peak response in responders | 8 to 12 weeks | Decision point on second injection or alternative care |
| Maintenance consideration | 6 to 12 months in responders | Only if first series produced meaningful benefit |
The most important point: a meaningful number of patients are non-responders. Patients who do not get clinical benefit from a complete first series are unlikely to benefit from indefinite repeat injections. That is not a failure of the injection — it is information that the disease is in a different category and a different approach is more appropriate.
Biologic injections are generally well-tolerated, but no procedure is risk-free. The risks reviewed at consultation include:
The three concerns we hear most often before biologic injection consultation, with honest answers:
No. PRP, BMAC, Lipogems, hyaluronic acid, and cortisone do not fix knee arthritis — arthritis is cartilage thinning that adult tissue does not regrow, and no injectable biologic has been shown to regenerate cartilage in adult arthritic knees. The honest realistic ceiling for biologic injection in mild to moderate knee OA is symptom modification — reduced pain, sometimes for several months at a time — in selected patients. That can be meaningful, but it is not a fix and not a cure. Patients who arrive expecting cartilage regeneration leave disappointed even when they get real symptom relief.
PRP, BMAC, and Lipogems are generally classified as investigational by commercial insurers because of heterogeneous preparation methods, mixed clinical-trial outcomes, and absence of FDA approval as drugs for specific orthopedic indications. Hyaluronic acid is FDA-approved for symptomatic knee OA and is generally covered with prior authorization; cortisone is covered. The cost of out-of-pocket biologic injections should be weighed against realistic expectations of benefit before deciding to proceed — particularly if a less expensive evidence-based option (structured PT, weight optimization, hyaluronic acid where indicated) has not yet been fully tried.
It depends on which injection. PRP contains essentially no stem cells — it is concentrated platelets from your own blood. BMAC and Lipogems contain a fraction of mesenchymal stromal cells (more accurate than calling them "stem cells") from your own bone marrow or fat. Many cash-pay clinics market amniotic-derived or umbilical-cord-derived "stem cell" injections that are not what an academic orthopedic practice means by biologic injection — those products contain few if any viable stem cells after processing, are not FDA-approved for orthopedic use, and have been the subject of FDA warnings. If a clinic is using "stem cell" language without being specific about what tissue type, where it came from, and how it was processed, that is a reason for skepticism, not enthusiasm.
The insurance picture is uneven across biologic injection options:
Before any out-of-pocket biologic injection, our office reviews the realistic expectations and the cost in advance, in writing. If a less expensive evidence-based option has not yet been tried — structured PT, weight optimization, NSAIDs, bracing, hyaluronic acid where appropriate — the right answer is often to start there. For benefits verification on covered injections (cortisone, hyaluronic acid), call us at (646) 960-7227 or contact the office.
A sub-specialty second opinion with a board-certified orthopedic surgeon is particularly worth seeking when:
Dr. Strickland sees patients at two offices, both of which work with patients traveling in from outside the immediate area:
Many out-of-state patients travel to HSS specifically for second opinions on biologic injection claims made by other clinics, for chronic patellar tendinopathy that has failed local care, and for honest evidence-graded discussion of where biologics do and do not fit in a comprehensive treatment plan.
The clinical positions on this page are grounded in Dr. Strickland's published patient education on biologics, the broader HSS sub-specialty consensus on the role of orthobiologic injections in knee care, and current FDA and professional-society regulatory framing. The literature is intentionally limited — reflecting the limited evidence base and the many open questions in this space:
| Topic | Grounding source on this site | What it informs |
|---|---|---|
| PRP for ACL healing | Orthobiologics study: can ACLs heal faster using PRP? | Research-stage framing of PRP as an ACL adjunct; not standard of care |
| Amniotic suspension allograft (ASA) injections for knee OA | HSS research study on ASA injections for knee OA | Investigational status of amniotic-derived injectables; distinct from cash-pay "stem cell" marketing |
| Stem cells, exosomes, and cartilage repair | Stem cells, exosomes & cartilage repair | Dr. Strickland's broader commentary on stem-cell biology and the gap between marketing and evidence |
| "Dancing molecules" cartilage research | Northwestern dancing-molecules research | Animal-model regenerative work; promising and research-stage, not a current clinical option |
| Sea coral / CartiHEAL scaffold | Sea coral helps knee osteoarthritis (CBS News) | Emerging cartilage scaffold technology; not a biologic injection |
| Honest framing of emerging arthritis treatments | Knee arthritis — emerging treatments section | Tone match: emerging biologics are research-stage, not standard of care |
| Surgeon credentials and experience | About Dr. Sabrina Strickland | HSS sub-specialty care, board certification, and the basis for "Medically reviewed by" |
The honest summary the literature supports: biologic injections are adjunctive, not primary, treatments for the knee. The evidence is strongest for chronic patellar tendinopathy after failed PT, mixed for mild knee OA, and absent for cartilage regeneration. Anything beyond that — particularly cash-pay-clinic claims of arthritis cure or stem-cell knee regeneration — is marketing, not medicine.
No. PRP does not cure knee arthritis, and no injectable biologic has been shown to regenerate functional hyaline cartilage in adult arthritic knees. The evidence-based role of PRP for knee osteoarthritis is symptom modification, not structural cure — and even that benefit is mixed in the literature. In well-selected patients with mild to moderate arthritis, a series of PRP injections may reduce pain and delay further intervention; in many other patients, PRP produces no meaningful benefit at all. Patients should be skeptical of any clinic — particularly cash-pay clinics not led by board-certified orthopedic surgeons — that promises cartilage regeneration or arthritis cure from PRP, BMAC, Lipogems, or "stem cell" injections.
No. PRP (platelet-rich plasma) is a concentrate of platelets prepared from your own blood; it contains essentially no stem cells. BMAC (bone marrow aspirate concentrate) and Lipogems contain a fraction of mesenchymal stromal cells, sometimes loosely called "stem cells," from your own bone marrow or fat. Many cash-pay "stem cell" clinics market amniotic-derived or umbilical cord-derived products that contain few if any viable stem cells after processing — these are not what an academic orthopedic practice means by biologic injection. The FDA has issued warnings about some of these products and clinics. None of these injections — PRP, BMAC, Lipogems, or amniotic-derived products — has been shown to regenerate cartilage in adult arthritic knees.
PRP is generally classified as investigational by commercial insurers for orthopedic indications and is paid out of pocket. The reasons commonly cited include heterogeneous preparation methods, mixed clinical-trial outcomes, and absence of FDA approval as a drug or device for specific orthopedic indications (PRP is regulated as a blood derivative, not approved for a labeled clinical use). BMAC and Lipogems are also typically out of pocket. Hyaluronic acid is generally covered by insurance for documented knee osteoarthritis after a trial of more conservative measures; cortisone is covered. Cost should be weighed honestly against realistic expectations of benefit before proceeding with any out-of-pocket biologic injection.
In responders, the clinical effect of a PRP series typically becomes apparent at 4 to 12 weeks and may persist for several months to a year before retreatment is considered. A meaningful number of patients are non-responders — they get little or no benefit even from a complete series. Patients who do not respond after the first series are unlikely to benefit from indefinite repeat injections; at that point the conversation should turn to other evidence-based options. PRP does not "last forever" and does not modify the underlying joint structure.
The best-evidenced indication for PRP at the knee is chronic patellar tendinopathy ("jumper's knee") that has failed structured eccentric loading rehabilitation. PRP for mild knee osteoarthritis is a reasonable adjunctive option in selected patients who have well-preserved alignment, no major mechanical symptoms, realistic expectations, and who have already engaged with structured PT and weight optimization. PRP is not appropriate for advanced bone-on-bone arthritis, severe malalignment, mechanical symptoms from a torn meniscus or loose body, or as a substitute for cartilage repair when a focal cartilage defect is present. Patients seeking cartilage regeneration are not good candidates — biologics do not regenerate cartilage.
Yes. PRP is concentrated platelets from your own blood. BMAC (bone marrow aspirate concentrate) is bone marrow drawn from your iliac crest, processed, and injected — it contains a stem-cell-rich fraction along with growth factors. Lipogems uses a small liposuction sample of your own fat, processed at the bedside, and injected; it contains cellular and structural fat including mesenchymal stromal cells. The evidence base for BMAC and Lipogems is less mature than for PRP and hyaluronic acid. Both are generally out-of-pocket. Like PRP, they are symptom-modifying at best in selected patients — none regenerates cartilage.
Repeated cortisone injections in arthritic joints have been associated with cartilage thinning in some published studies, and cortisone is best used selectively for acute flares or as a bridge in end-stage disease — not as an indefinite "every three months" routine. For joint-preservation candidates earlier in the disease course, hyaluronic acid, PRP, structured PT, weight optimization, or — when imaging supports it — joint-preserving surgery may be more appropriate than repeated cortisone. The right answer depends on the stage of disease and the patient's overall plan.
Yes. Stem cell therapy as marketed by many cash-pay clinics is not FDA-approved for orthopedic use, and claims of cartilage regeneration in adult arthritic knees are not supported by current evidence. The FDA has issued warnings about some amniotic and umbilical "stem cell" products. If a non-surgeon-led clinic is promising to cure your arthritis, regrow cartilage, or replace knee replacement with an injection, those claims should prompt a sub-specialty second opinion with a board-certified orthopedic surgeon — not a deposit on an injection package. Legitimate biologic care uses your own tissue, frames the role honestly as adjunctive rather than curative, sits inside a comprehensive treatment plan, and does not promise outcomes.
Dr. Strickland approaches PRP and biologic injections as adjunctive options that may be discussed within a comprehensive treatment plan — not as a primary therapy and not as a substitute for evidence-based care. Strongest evidence for chronic patellar tendinopathy after failed PT; reasonable adjunct in selected patients with mild knee osteoarthritis; not appropriate for advanced arthritis, cartilage replacement, or as a substitute for surgery when surgery is indicated. Her position is neither dismissive nor over-promised: the right injection in the right patient at the right stage of disease can produce meaningful symptom relief; the wrong injection in the wrong knee is an expensive way to delay better treatment.
For the full knee arthritis treatment ladder, see knee arthritis. For chronic patellar tendinopathy — the strongest knee indication for PRP — see anterior knee pain and patellar pain and patellofemoral arthritis. For the evidence-based options for focal cartilage damage (where biologic injection is not the right answer), see MACI cartilage repair and cartilage transplantation (OATS & allograft). For alignment correction in isolated compartment OA, see joint preservation and osteotomy. For sports-medicine context including return-to-sport considerations, see sports injuries. For PRP as a research-stage adjunct in ACL healing, see ACL tear surgery. For partial and total knee replacement when joint-preserving options have been exhausted, see Mako robotic-assisted surgery.
Medical Disclaimer. This content is for informational purposes only and does not constitute medical advice, diagnosis, or treatment. PRP and other biologic injections are adjunctive options that may be discussed within a comprehensive treatment plan and are not a substitute for evaluation and care by a board-certified orthopedic surgeon who has reviewed your imaging, history, and physical examination. No biologic injection has been shown to regenerate cartilage in adult arthritic knees, and a meaningful number of patients receive no clinical benefit from a complete series of injections. Individual outcomes vary based on indication, stage of disease, alignment, prior care, comorbidities, and adherence to structured rehabilitation. Emerging and research-stage treatments referenced on this page are not standard of care and are not offered or recommended as substitutes for evidence-based treatment.
If you are considering PRP for chronic patellar tendinopathy or mild knee OA — or have been told by a cash-pay clinic that "stem cells" can replace surgery and want a sub-specialty second opinion — bring your imaging to a consultation in NYC or Stamford, CT.
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