How Long Does Regenerative Medicine Take to Work?

Regenerative procedures are measured in months, not days. For platelet-rich plasma (PRP) in the knee, the highest-quality trials track change at 1, 3, 6 and 12 months, and the clearest gains over placebo appear at 3 to 6 months (Bensa et al., 2025). Cell-based procedures are studied on a similar or longer timeline, with 12 months as the standard follow-up point (Rahmadian et al., 2025). Anyone who promises relief in a few days is describing something the research does not measure.

What This Means

A cortisone injection contains a steroid and often a local anesthetic, so pain can drop within hours. Regenerative procedures work differently. PRP concentrates platelets from your own blood; bone marrow concentrate and other cell-based products contain cells and signaling proteins. These are injected to support the local tissue environment, and any change in symptoms depends on biological processes that unfold over weeks (Mayo Clinic Orthopedics & Sports Medicine, n.d.).

That is why the first week after a regenerative injection is often unremarkable or even a little worse. Soreness and a temporary flare at the injection site are common, and they are not a sign that the procedure failed. The window that matters clinically is roughly weeks 4 through 24.

It also matters what "work" means. In research, PRP and cell-based procedures for knee osteoarthritis are judged on validated scales such as the WOMAC index (a questionnaire on pain, stiffness and function) and a 0-to-10 pain score. A meaningful result is a change large enough that a patient would notice it, not just a statistically significant number.

Candidacy

The timeline is part of candidacy. Someone who needs to be functional for a specific event in two weeks is not well matched to a procedure whose measured effect starts at month one or later. Someone with months of stable, activity-limiting joint pain who has already tried conservative care is closer to the population the trials enrolled.

Candidacy is decided by a licensed physician after an in-person evaluation. Factors that influence it include the diagnosis, the stage of joint change on imaging, medications such as blood thinners or anti-inflammatories that may need to be paused, active infection, and realistic goals. No one is promised a result or a date.

Clinical Evaluation

An evaluation at PrimeCell Regenerative includes a musculoskeletal and neurological exam, a review of prior imaging, and diagnostic ultrasound when appropriate. The goal is to identify which structure is generating the pain before any option is discussed, because the timeline for a tendon differs from the timeline for an arthritic joint.

Baseline measurements are recorded at that visit: a pain score, a function score, and the activities that are currently limited. Those numbers are what progress is compared against at 6 weeks, 3 months and 6 months. Without a baseline, "is it working" becomes a guess.

Available Options

Conventional care comes first and has the strongest evidence. The American Academy of Orthopaedic Surgeons (AAOS) 2021 guideline gives strong recommendations for supervised or unsupervised exercise, patient education, self-management programs, topical and oral NSAIDs, and acetaminophen for knee osteoarthritis, and a moderate recommendation for sustained weight loss in overweight patients (AAOS, 2021). Intra-articular corticosteroids may provide short-term relief, while routine hyaluronic acid injections are not recommended (AAOS, 2021). Joint replacement remains the definitive option for advanced disease.

Regenerative options are considered alongside, not instead of, that care. They include PRP, bone marrow aspirate concentrate, and other cell-based or exosome products. Academic programs such as Mayo Clinic Orthopedics & Sports Medicine describe these as minimally invasive, ultrasound-guided outpatient procedures performed under local anesthesia (Mayo Clinic Orthopedics & Sports Medicine, n.d.).

Stem cell, exosome and similar cellular products are investigational outside FDA-approved clinical trials. They are not FDA-approved to diagnose, cure, mitigate, treat or prevent any disease or condition, including osteoarthritis, tendon injuries or back pain (U.S. Food and Drug Administration, 2024).

Benefits, Limitations and Risks

The potential benefit is a reduction in pain and improvement in function that, in trials of PRP, lasted through 6 to 12 months in many participants (Shen et al., 2017). PRP uses your own blood and, across randomized trials, did not significantly increase post-injection adverse events compared with other injections (Shen et al., 2017).

The limitations are real. Not everyone responds, response size varies with the product (platelet concentration changed outcomes in the PRP data), and the effect is not permanent. These procedures are typically paid out of pocket. Nothing about them "regrows cartilage" or replaces surgery when surgery is indicated.

Risks with any injection include pain, bleeding, infection and, rarely, nerve injury. The FDA has received reports of blindness, tumor formation, serious infections and unwanted immune reactions following unapproved cell and tissue products, and warns that a product being listed on clinicaltrials.gov or "registered with FDA" does not mean it is legally marketed (U.S. Food and Drug Administration, 2024). Ask which product is being used, how it is processed, and under what regulatory pathway.

What the Evidence Shows

What the evidence does establish: a 2025 meta-analysis of 18 randomized trials (1,995 patients) found PRP statistically superior to placebo for knee osteoarthritis pain and function at every follow-up point, with improvement exceeding the threshold patients can perceive at 3 and 6 months for pain and at 1, 3, 6 and 12 months for function (Bensa et al., 2025). An earlier review of 14 trials (1,423 patients) found PRP significantly reduced WOMAC pain and improved function at 3, 6 and 12 months compared with saline, hyaluronic acid, ozone or corticosteroid injections (Shen et al., 2017). For cell-based products, a 2025 meta-analysis of six randomized trials (300 patients) found a single intra-articular mesenchymal stem cell injection improved WOMAC scores at 12 months, with doses of 25 million cells or fewer showing benefit and higher doses adding nothing (Rahmadian et al., 2025).

What the evidence does not establish: how any individual patient will respond; a direct comparison of one product against another; durability beyond 12 months; whether the underlying disease is changed rather than the symptoms; and whether a product prepared in one clinic behaves like the product studied in a trial. Many of the underlying trials carried moderate or high risk of bias (Shen et al., 2017). The evidence base for tendons, spine and hip is thinner than for the knee, and the evidence for exosomes in orthopedics is early.

Recovery / Next Steps

A realistic timeline for a joint injection looks like this. Days 1 to 7: expect soreness and a possible flare; most people limit heavy loading for a few days. Weeks 2 to 6: the first changes, if any, tend to appear; a follow-up visit checks the baseline scores. Months 3 to 6: the window where trials show the largest measured difference. Month 12: the standard endpoint for judging durability and whether a repeat procedure is reasonable.

Two practical rules. First, judge the result against your baseline numbers, not against how you felt yesterday. Second, if nothing has changed by three months, that is a reason to reassess the diagnosis and the plan, not to repeat the same injection.

Orlando Considerations

Orlando patients are often active year-round, so the early-weeks activity restriction gets more attention here than the procedure itself. Plan the injection around travel, golf, running or work that requires prolonged standing, and keep the 6-week and 3-month follow-up visits on the calendar. Physicians performing these procedures in Florida are licensed through the Florida Board of Medicine; confirm that the person doing the injection is the physician who evaluated you.

Frequently Asked Questions

Why do I feel worse the first few days after a PRP injection?

A temporary flare is common because the injection itself provokes a local response and there is no steroid or long-acting anesthetic in it. It usually settles within a week.

How many injections will I need?

Trial protocols range from a single injection to a series of two or three spaced weeks apart. The number depends on the product, the joint and the response at follow-up, and is decided by your physician.

How long do the results last?

In PRP trials for knee osteoarthritis, benefit was measured through 12 months in many participants, but it faded in some, and follow-up beyond a year is limited. Results vary and no duration is guaranteed.

Is a faster-acting option available if I need relief now?

Yes. A corticosteroid injection can provide short-term relief within days, and oral or topical anti-inflammatories are guideline-supported. Which option fits is decided at the evaluation.

Can I combine regenerative injections with physical therapy?

Exercise carries the strongest recommendation in the AAOS guideline, and it is commonly continued alongside an injection. Your physician will set the timing.

Stem cell, exosome and other cellular products are investigational outside FDA-approved clinical trials and are not FDA-approved to diagnose, cure, mitigate, treat, or prevent any disease or condition.

This article is for educational purposes only and is not medical advice. Individual results vary, and any decision to pursue a regenerative procedure should be made after a full evaluation with a licensed physician who can review your specific history, alternatives, and risks.

Medically reviewed by Kenny Chantasi, DO.

References

American Academy of Orthopaedic Surgeons. (2021). Management of osteoarthritis of the knee (non-arthroplasty): Evidence-based clinical practice guideline (3rd ed.). https://www.aaos.org/quality/quality-programs/osteoarthritis-of-the-knee/

Bensa, A., Previtali, D., Sangiorgio, A., Boffa, A., Salerno, M., & Filardo, G. (2025). PRP injections for the treatment of knee osteoarthritis: The improvement is clinically significant and influenced by platelet concentration: A meta-analysis of randomized controlled trials. The American Journal of Sports Medicine, 53(3), 745–754. https://doi.org/10.1177/03635465241246524

Mayo Clinic Orthopedics & Sports Medicine. (n.d.). Regenerative medicine. Mayo Foundation for Medical Education and Research. https://sportsmedicine.mayoclinic.org/service/regenerative-medicine/

Rahmadian, R., Ariliusra, Z., Kusuma, K. R. A., Ali, H., Raymond, B., & Meksiko, R. (2025). Efficacy of a single intra-articular injection of mesenchymal stem cells for knee osteoarthritis: A dose-focused meta-analysis of randomized controlled trials. Journal of Orthopaedic Surgery and Research. https://doi.org/10.1186/s13018-025-06190-4

Shen, L., Yuan, T., Chen, S., Xie, X., & Zhang, C. (2017). The temporal effect of platelet-rich plasma on pain and physical function in the treatment of knee osteoarthritis: Systematic review and meta-analysis of randomized controlled trials. Journal of Orthopaedic Surgery and Research, 12, 16. https://doi.org/10.1186/s13018-017-0521-3

U.S. Food and Drug Administration. (2024, April 8). Important patient and consumer information about regenerative medicine therapies. https://www.fda.gov/vaccines-blood-biologics/consumers-biologics/important-patient-and-consumer-information-about-regenerative-medicine-therapies

Last medically reviewed: September 2, 2026.

If joint pain has limited you for months and you want a realistic timeline before deciding anything, that is what a consultation is for. Schedule an evaluation and bring prior imaging and records if you have them.

Related reading

• What Is Regenerative Medicine Used For?
• How Long Is Recovery After Stem Cell Therapy?
• How Long Does It Take to See Results From Exosome Therapy?
• How Do You Know If You’re a Good Candidate for Regenerative Medicine?

More questions answered on the PrimeCell patient blog, or see frequently asked questions.

Related services at PrimeCell

PrimeCell is a physician-led practice in Orlando. Candidacy for any procedure is determined at an in-person evaluation.