Prolotherapy for Knee Pain: Evidence, Protocols, and What to Expect

A prolo injection for the knee, formally called prolotherapy, is a series of hypertonic dextrose injections (usually 12.5 to 25% dextrose mixed with lidocaine) given into the knee joint and at the ligament and tendon attachments around it to prompt a local repair response. In a 2013 randomized trial of 90 adults with knee osteoarthritis, Rabago and colleagues at the University of Wisconsin found that dextrose prolotherapy improved pain, function and stiffness scores more than saline injections or home exercise at 52 weeks.

Knee pain is one of the most common reasons people seek out prolotherapy. The knee takes an enormous load over a lifetime, and conventional options for knee osteoarthritis often feel like a choice between “not enough” (physical therapy and anti-inflammatories) and “too much” (total knee replacement).

Prolotherapy occupies a middle ground that appeals to many patients: a relatively simple injection procedure that aims to stimulate the body’s own repair processes, potentially delaying or avoiding surgery. The sections below cover what the evidence says, who responds best, what a session and a full course involve, and how prolotherapy for the knee compares with cortisone, hyaluronic acid and platelet-rich plasma (PRP) injections.

What Is a Prolo Injection for the Knee?

“Prolo injection” is the everyday name for prolotherapy, also called proliferation therapy, proliferative injection therapy or regenerative injection therapy (RIT). The term was coined by the American surgeon George Hackett in the 1950s, who used irritant injections to treat lax ligaments and tendons. In the knee, the word now almost always means dextrose prolotherapy (DPT).

The injected solution is called a proliferant. Hypertonic dextrose is by far the most common choice today. Older and less common solutions include sodium morrhuate, a fatty acid extract, and P2G, a mix of phenol, glycerin and glucose.

Dextrose itself is an FDA approved drug, but no prolotherapy solution is FDA approved to treat knee osteoarthritis or knee pain. Clinicians who offer it are using dextrose off label, which is legal and common in medicine, and it is one reason insurers decline to pay for it.

Which knee conditions is it used for?

Clinicians use knee prolotherapy most often for osteoarthritis of the knee, particularly mild to moderate disease. Other common indications are sprained or lax collateral ligaments, chronic knee instability, patellar tendinopathy, pes anserine pain on the inner knee, and persistent joint pain that has not settled with exercise therapy.

How Prolotherapy Works in the Knee

Prolotherapy, short for “proliferant therapy”, works by injecting an irritant solution (most commonly dextrose at 12.5-25% concentration) into damaged or degenerated tissues. In the knee, injections target multiple structures:

• Intra-articular space: Directly into the joint capsule to address cartilage degeneration and synovial inflammation
• Collateral ligaments: The medial collateral ligament (MCL) and lateral collateral ligament (LCL) at their attachment points
• Patellar tendon: At the tibial tuberosity and patellar attachments
• Surrounding entheses: Where tendons and ligaments attach to bone around the knee

The dextrose solution triggers a localized inflammatory cascade that recruits growth factors, fibroblasts, and other healing cells to the injection site. Over a period of weeks, this leads to collagen deposition, tissue strengthening, and in the case of intra-articular injections, potential improvement in the joint environment.

Researchers have also proposed a second, more direct effect: dextrose may calm irritated sensory nerves around the joint, which could explain why some patients report pain relief before any tissue change would be expected. This mechanism is still a hypothesis rather than an established finding.

A typical knee prolotherapy session involves 10-20 individual injection points around the knee, covering both the intra-articular space and the periarticular soft tissues. This full approach distinguishes prolotherapy from single-injection therapies like cortisone or hyaluronic acid.

The Evidence: What Do the Studies Show?

Prolotherapy for knee osteoarthritis has one of the stronger evidence bases in the prolotherapy literature. Several key studies stand out:

The Rabago Trials

Dr. David Rabago and colleagues at the University of Wisconsin have conducted the most rigorous trials of dextrose prolotherapy for knee OA:

• Rabago et al. (2013), Annals of Family Medicine: A randomized controlled trial of 90 adults with knee OA compared dextrose prolotherapy to saline injections and at-home exercise. The prolotherapy group showed significantly greater improvements in WOMAC pain, function, and stiffness scores compared to both control groups at 52 weeks. Improvements were clinically meaningful and sustained. Injections were given at weeks 1, 5 and 9, with optional extra sessions at weeks 13 and 17, and the composite WOMAC score improved by 15.3 points with dextrose against 7.6 with saline and 8.2 with exercise. The authors reported no adverse events (Rabago et al., 2013).
• Rabago et al. (2012), complementary study: Demonstrated improvements in patient-reported knee-specific quality of life and overall function with dextrose prolotherapy.

The Hong Kong Saline-Controlled Trial

Sit and colleagues, with Rabago as a coauthor, ran a blinded trial in a university primary care clinic in Hong Kong. They randomized 76 adults with knee osteoarthritis to intra-articular dextrose or normal saline at weeks 0, 4, 8 and 16.

At 52 weeks, the dextrose group’s WOMAC pain score had improved by about 10 points more than the saline group’s on a 100-point scale, with similar gains in function and quality of life and no reported adverse events (Sit et al., 2020). Because this trial injected only inside the joint, it suggests the intra-articular injection carries part of the benefit on its own.

Cochrane and Systematic Reviews

A systematic review and meta-analysis published in the Journal of Alternative and Complementary Medicine (2017) analyzed available RCTs and concluded that dextrose prolotherapy provided clinically meaningful improvements in pain, function, and stiffness for knee OA when compared to control interventions. The effect sizes were moderate, and the treatment was well-tolerated.

The Cochrane Collaboration has noted that while the evidence is promising, more large-scale, multi-center trials with longer follow-up are needed to establish prolotherapy as a standard treatment recommendation.

Where the Evidence Is Thin

Most knee prolotherapy trials enrolled fewer than 100 people and were run at a small number of academic centers. Injection sites, dextrose strength and the number of sessions differ from trial to trial, so the results describe a family of protocols rather than one standard treatment.

No trial has shown that dextrose rebuilds cartilage you can see on imaging. Head-to-head comparisons with PRP and hyaluronic acid are few and small, and very little is known about results beyond two to three years.

Key Findings Across Studies

Prolotherapy vs. Other Knee Injections

If your doctor has discussed injection options for your knee, you have probably heard about cortisone and hyaluronic acid (viscosupplementation). Here is how dextrose prolotherapy compares:

One of the most compelling arguments for prolotherapy over cortisone is the long-term safety profile. A 2017 randomized trial in JAMA by McAlindon and colleagues found that intra-articular triamcinolone given every 12 weeks for 2 years was associated with greater cartilage volume loss in knee OA than saline injections, with no significant difference in knee pain (McAlindon et al., 2017). Prolotherapy, by contrast, aims to promote tissue repair rather than suppress it.

Prolotherapy vs. PRP and Stem Cell Injections

Platelet-rich plasma (PRP) is the injection most often weighed against prolotherapy. PRP concentrates growth factors from your own blood, while prolotherapy uses an inexpensive dextrose solution to provoke the body into releasing its own. PRP sessions usually cost more per injection, and the small trials that compare the two for knee osteoarthritis have not settled which works better. Our side-by-side breakdown of prolotherapy vs. PRP covers the trade-offs in more detail.

Stem cell and bone marrow concentrate injections sit at the far end of cost and regulatory uncertainty. The FDA has not approved any stem cell product for knee osteoarthritis, and the evidence for these injections is thinner than the dextrose prolotherapy trials described above.

The Prolotherapy Protocol for Knee Pain

A typical prolotherapy treatment course for knee pain follows four stages: an initial evaluation, a series of injection sessions, a course of 4 to 6 sessions spaced weeks apart, and a short recovery after each visit.

Initial Evaluation

Your practitioner will review imaging (X-rays, possibly MRI), perform a physical examination assessing ligament stability, joint line tenderness, and range of motion, and take a detailed history of your knee symptoms. This evaluation determines the injection strategy and sets realistic expectations.

The Injection Session

• Solution: Most commonly 12.5-25% dextrose (higher concentrations for intra-articular, lower for periarticular structures)
• Volume: 30-60 mL total across all injection points
• Injection sites: 10-20 points including the joint space, medial and lateral collateral ligaments, patellar tendon attachments, and pes anserinus
• Guidance: Some practitioners use ultrasound guidance for intra-articular injections; periarticular injections are typically done by palpation
• Duration: 15-30 minutes for the injection procedure itself
• Anesthesia: Typically includes lidocaine mixed with the dextrose solution; some practitioners use a separate local anesthetic

Treatment Course

• Number of sessions: 4-6 sessions for most patients; some need up to 8
• Spacing: Every 3-6 weeks between sessions
• Total duration: 3-9 months to complete treatment
• Response assessment: Most practitioners evaluate progress after 3 sessions to determine whether to continue

Post-Injection

• Expect increased pain and swelling for 2-5 days after each session, this is the intended inflammatory response
• Avoid NSAIDs (ibuprofen, naproxen) for 2-3 days after treatment, as they counteract the therapeutic inflammation
• Acetaminophen (Tylenol) is permitted for pain management
• Light activity is encouraged; avoid heavy exercise for 3-5 days
• Ice is typically discouraged in the first 24-48 hours (to allow the inflammatory response); some practitioners allow it after that

Most clinicians pair the injections with a strengthening program for the quadriceps and hip muscles, because exercise therapy remains the foundation of knee osteoarthritis care. The guide to arthritis treatment options explains how injections fit alongside exercise, weight management and bracing.

Who Responds Best to Knee Prolotherapy?

Not everyone with knee pain is a good candidate for prolotherapy. Based on the evidence and clinical experience, the best responders tend to be:

• Mild-to-moderate knee OA (Kellgren-Lawrence grade 1-3), there is still functional cartilage and joint space remaining
• Ligament laxity or instability, the knee “gives way” or feels unstable, particularly with MCL or LCL involvement
• Younger patients (under 65) who want to delay or avoid joint replacement
• Active individuals whose pain limits function but who are otherwise healthy
• Patients who have failed physical therapy and bracing but are not ready for surgery
• Those willing to commit to the full 4-6 session course rather than expecting one-injection results

If you are still working out whether your symptoms point to osteoarthritis, our overview of knee osteoarthritis symptoms and stages explains the Kellgren-Lawrence grades referred to above.

When NOT to Use Prolotherapy for the Knee

Prolotherapy is unlikely to be effective and may not be appropriate in these situations:

• Severe bone-on-bone OA (Kellgren-Lawrence grade 4): When there is no remaining joint space and bone is articulating directly with bone, prolotherapy cannot regenerate sufficient cartilage to restore joint function. Joint replacement is typically the appropriate intervention at this stage.
• Acute meniscal tears requiring surgical repair: A locked knee from a bucket-handle meniscal tear needs arthroscopic surgery, not injection therapy.
• Active joint infection: Injecting into an infected joint is contraindicated.
• Inflammatory arthritis (active RA, gout flare): The underlying disease process requires systemic treatment, not local injection. Active rheumatoid arthritis is managed by a rheumatologist with disease-modifying drugs.
• Unrealistic expectations: Prolotherapy aims to reduce pain and improve function in people who respond, it does not restore the knee to its 20-year-old state.

Side Effects and Risks of Knee Prolotherapy

The most common side effect of knee prolotherapy is a flare of pain, swelling and stiffness that lasts 2 to 5 days after each session. This flare is the inflammatory response the treatment is designed to provoke. Bruising and tenderness at the injection points are also common.

Less common risks are the ones shared by any joint injection: infection, bleeding, a reaction to the local anesthetic and, rarely, irritation of a nearby nerve. Both the 2013 Rabago trial and the 2020 Sit trial reported no adverse events, although trials of this size cannot rule out rare complications.

Tell your clinician if you have diabetes, take blood thinners, or have a bleeding disorder, a skin infection near the knee or an allergy to lidocaine. A clinician who checks these points before injecting is a good sign.

How Much Does Knee Prolotherapy Cost?

Knee prolotherapy typically costs $200 to $600 per session, and a full course of 4 to 6 sessions usually totals $800 to $3,600. The price depends on the region, the type of clinician, whether ultrasound guidance is used, and how many structures around the knee are injected.

Medicare’s national coverage policy lists prolotherapy as a non-covered service, and most commercial insurers classify it as investigational. Ask for the full course price in writing before the first session, and ask whether follow-up visits and imaging are included.

Who Offers Knee Prolotherapy and How to Find a Clinic

Knee prolotherapy is performed mainly by physiatrists (physical medicine and rehabilitation physicians), sports medicine physicians, osteopathic physicians (DOs) and family medicine physicians, along with some orthopedic and pain medicine specialists. In some states, licensed naturopathic physicians also perform it within their scope of practice.

Before booking, these five questions help separate a careful practice from a casual one:

1. How many knee prolotherapy courses do you perform, and for which diagnoses?
2. Do you use ultrasound guidance for the injection into the joint?
3. Which dextrose concentration and which injection sites will you use for my knee?
4. How will you measure progress, and when will we decide whether to continue?
5. What is the total cost of the course, and what happens if I have not improved after three sessions?

Clinics that offer prolotherapy often also provide PRP and arthritis care, so the national directory of clinics offering arthritis treatment and the list of PRP injection providers are practical places to start. Confirm on the clinic profile or by phone that prolotherapy itself is offered. For background on the treatment across other joints, the prolotherapy treatment guide covers indications, solutions and safety.

Listing order on Regenerated.com is not paid ranking. Featured slots are clearly labeled and capped, and Verified means a clinic has completed credential checks, not that it paid for placement. The directory is free for patients, and inclusion in it is not an endorsement. The guide to Featured, Verified and organic listings explains each label.

Frequently Asked Questions

What is a prolo injection in the knee?

A prolo injection in the knee is prolotherapy: a series of hypertonic dextrose injections, usually 12.5 to 25% dextrose mixed with lidocaine, placed inside the knee joint and at the ligament and tendon attachments around it. The mild irritation is meant to trigger a local repair response. A session usually covers 10 to 20 injection points, and most courses run 4 to 6 sessions spaced 3 to 6 weeks apart.

How many prolotherapy injections does a knee need?

Most people receive 4 to 6 knee prolotherapy sessions spaced 3 to 6 weeks apart, and some need up to 8. Each session involves 10 to 20 individual injections around the joint. In the 2013 Rabago trial, patients had injections at weeks 1, 5 and 9, with optional sessions at weeks 13 and 17. Many clinicians reassess after 3 sessions to decide whether continuing is worthwhile.

How painful are prolotherapy injections in the knee?

Most patients describe knee prolotherapy injections as moderately uncomfortable rather than severely painful. The injection into the joint usually feels like pressure and an ache, while injections at the ligament attachments cause a brief, sharp sting at each point. Lidocaine mixed into the dextrose numbs the area within minutes. Expect the knee to be sore, stiff and swollen for 2 to 5 days after each session, with a return to normal daily activity within a few days.

Can prolotherapy regrow knee cartilage?

No good evidence shows that prolotherapy regrows knee cartilage in humans. Animal studies and small human studies suggest that intra-articular dextrose may improve the joint environment and possibly slow cartilage breakdown, but no trial has shown meaningful new hyaline cartilage on imaging. The pain and function gains seen in trials more likely come from stronger ligament and tendon attachments, calmer pain signaling and better joint mechanics.

Is prolotherapy covered by insurance for knee pain?

Usually not. Medicare and most commercial insurance plans classify prolotherapy as experimental or investigational and do not pay for it. A few practitioners provide a superbill for possible partial out-of-network reimbursement, but approval is uncommon. Expect to pay out of pocket: a full knee course of 4 to 6 sessions typically costs $800 to $3,600, depending on the practitioner, the region and whether ultrasound guidance is used.

How long do prolotherapy results last for knee pain?

In the Rabago trial, improvements in knee pain, function and stiffness were sustained at the 52-week follow-up, and an observational extension suggested benefits persisting at 2.5 years. Prolotherapy does not halt the underlying osteoarthritis, so some patients return for 1 to 2 maintenance sessions a year. Results tend to last longest in people who keep up strengthening exercise, manage their weight and protect the joint.

Related Reading

This article is part of our thorough guide to prolotherapy. For a broader overview of how prolotherapy works, what conditions it treats, and how to find a qualified practitioner, see our pillar article: Prolotherapy: The Complete Guide.

Readers comparing injection options for the same joint may also want the walkthrough of PRP injections for the knee, which covers the procedure, recovery and cost.