Knee Osteoarthritis: How Long Do PRP Injections Last? What the Latest Research Tells Us

Mr. Wang, in his sixties, used to enjoy a one-hour brisk walk in the park every morning. Lately, though, knee pain often forces him to stop after less than ten minutes. He has tried painkillers and had hyaluronic acid injections at the hospital, but the effect is always short-lived. A friend recommended PRP injections, describing how your own blood is drawn out and injected back into the knee, which sounds remarkable. But Mr. Wang’s first question is also the one most patients ask: does PRP really work? How long can it last? Is it just a new name for an old effect?

Researchers have actually debated this question for years. With the publication of two major systematic reviews in 2025, the answer about PRP’s effectiveness in treating knee osteoarthritis has become clearer than ever. Today we will gather these latest studies and explain, in plain language, whether PRP is worth considering.

What is PRP, and is it used to treat knee osteoarthritis?

PRP stands for platelet-rich plasma. The way it is prepared is not complicated: the patient’s blood is drawn, spun in a centrifuge to concentrate the platelets and plasma, and then injected back into the knee joint.

Platelets contain many growth factors and cytokines, substances that can regulate the inflammatory response and promote tissue repair. For knee osteoarthritis, the goal is not just temporary pain relief, but to improve the joint environment, slow the pace of degeneration, and give the patient longer-lasting relief.

Compared with conventional treatments, PRP has several distinctive features. Painkillers work quickly, but over the long term they can harm the kidneys and stomach; corticosteroid injections provide strong pain relief, but repeated injections can damage the joint; hyaluronic acid injections act like a lubricant, with limited effect. PRP offers an option that relies on the body’s own repair capacity. But how effective is it? That has to be answered by research data.

2025 study one: only high-concentration PRP delivers long-term benefit

In 2025, the American Journal of Sports Medicine published a meta-analysis by Bensa and colleagues. They collected 18 randomized controlled trials with a total of 1,995 patients, comparing PRP with placebo (saline injection) at different time points.

The results were very clear:

• At three to six months, PRP was clearly better than placebo in reducing pain and improving joint function.

• At twelve months, a key distinction emerged. The study divided PRP into high platelet concentration and low platelet concentration.

  • High-concentration PRP: pain continued to improve, and function (the ability to walk and go up and down stairs) also maintained a significant difference in the study — a change patients were more likely to notice.

  • Low-concentration PRP: the effect only lasted about six months, and after a year there was almost no difference from placebo.

In other words, not all PRP is the same. If the platelet concentration is not high enough, it may only be a short-lived hope. When the physician can ensure high-concentration PRP is used, the effect has a chance of genuinely lasting up to a year.

2025 study two: combining PRP with hyaluronic acid works better

In the same year, another meta-analysis by Gupta and colleagues, published in the Journal of Orthopaedic Surgery and Research, included 37 randomized controlled trials with a total of 5,089 patients, followed for at least one year and in some cases as long as five years. They compared different injection approaches: PRP alone, hyaluronic acid (HA) alone, corticosteroid (CS) alone, and various combinations.

The analysis presented the results as a ranking:

1. PRP + hyaluronic acid gave the best improvement in pain and function, and lasted the longest.

2. PRP alone was also better than hyaluronic acid or corticosteroid.

3. Hyaluronic acid + corticosteroid, or hyaluronic acid alone, gave a moderate effect.

4. Corticosteroid alone relieved pain quickly in the short term, but had the worst long-term effect, along with concerns about side effects.

This result tells us that if you are looking for long-term improvement, PRP alone is already good, but combining it with hyaluronic acid gives a more stable and longer-lasting effect.

The three questions patients ask most

1. Am I a good candidate for PRP?

In the research, PRP’s benefit appears mainly in early-to-moderate knee osteoarthritis. If the knee is already severely deformed with bone rubbing directly on bone, PRP can do little, and at that point joint replacement surgery may need to be considered.

2. Does a single injection work?

Most studies used one to three injections spaced a few weeks apart. High-concentration PRP can usually maintain its effect for around a year, but not everyone is the same. Some patients improve markedly, while others respond less well.

3. Does PRP have side effects?

Because the source is the patient’s own blood, the risk of allergy is very low. The most common discomfort is knee swelling and soreness for a few days after the injection, which usually resolves on its own. In studies, repeated corticosteroid injections have been associated with cartilage-related effects, whereas PRP is drawn from the patient’s own blood; whether it is more appropriate than other options depends on your individual situation and a discussion with your physician.

Don’t rely on injections alone: lifestyle is the long-term key

Medical research tells us PRP has its advantages, but in real life, if a patient relies entirely on injections while neglecting daily care, the effect will be greatly reduced.

The knee is one of the hardest-working joints in the body, bearing several times your body weight with every step. If you want to slow degeneration, the following directions matter:

• Maintain your weight: for every 1 kilogram you lose, the pressure on the knee while walking is reduced by nearly 4 kilograms. For knee osteoarthritis, weight loss is the most direct form of care.

• Exercise regularly: rather than rushing into running, choose low-impact activities such as swimming, brisk walking, and cycling, which train the thigh muscles while protecting the knee joint.

• Strength training: the quadriceps are the knee’s natural knee brace. Simple leg extensions and seated leg raises can improve stability.

• Avoid overuse: prolonged hiking, squatting, kneeling, and carrying heavy loads all speed up joint wear, so adequate rest is just as important.

Injections are like a booster shot, but daily life is what decides how far you can go.

PRP is worth considering, but choose wisely

The latest research gives us a clearer direction. For early-to-moderate knee osteoarthritis, studies suggest that high-concentration PRP may improve pain and function for some patients — in some cases maintained beyond a year — and that combining it with hyaluronic acid is associated with more stable long-term results in the pooled data. Responses still vary from person to person.

For patients who have not yet reached the joint replacement stage, PRP is an option worth discussing with a physician. It also helps to remember that weight control, muscle training, and daily habits all play a part in how far and how steadily you can walk. Combining appropriate treatment with day-to-day self-care generally gives the knee the best support.

If you or a family member are affected by knee degeneration, consider discussing with a physician whether PRP is appropriate for your situation. No injection is a cure-all, and results vary between individuals; whether PRP suits you depends on your condition and a professional assessment.

References

• Am J Sports Med. 2025;53(3):745–754.
• J Orthop Surg Res. 2025;20:227.

Further Reading

• Knee topic
• Prolotherapy topic
• PRP prolotherapy
• Pain management