Stem Cells for Knees: Promising Treatment or Hoax?

Medically Reviewed by Hansa D. Bhargava, MD on April 06, 2017
From the WebMD Archives

April 14, 2017 -- At 55, George Chung of Los Angeles could keep up with skiers decades younger, taking on difficult slopes for hours and hours. "Skiing was my passion," he says.

Then the pain started, and the bad news. He had severe osteoarthritis, the ''wear-and-tear'' type, in both knees. Doctors suggested surgery, but he chose instead an investigational treatment -- injections of stem cells. Two months after the first treatment, he was out of pain. "I had been in pain of various degrees for 6 years," he says.

Now, nine treatments and 3 years later, he is back to intense skiing. Last year, he also took up long-distance cycling, completed five double-century cycling rides, and earned the prestigious California Triple Crown cycling award.

george chungGeorge Chung

Treatments with stem cells -- which can grow into different types of cells -- are booming in the U.S., with an estimated 500 or more clinics in operation. Some clinics offer treatment for conditions ranging from autism to multiple sclerosis to erectile dysfunction, often without scientific evidence to support how well they work.

Treatment for knee arthritis is especially popular. It’s one type of osteoarthritis, which afflicts 30 million Americans. Fees vary, but $2,000 per treatment for knee arthritis is about average. Insurance companies usually deny coverage, although in rare cases they may cover it when done along with another, established procedure.

Many doctors and scientists view the growth of stem cell treatments as very promising. But that growth comes as the FDA debates whether to tighten regulations on stem cell clinics after recent reports of patients suffering severe damage from treatment. The only stem cell-based product approved by the FDA is for umbilical cord blood-derived stem cells for blood cancers and other disorders.

In an editorial published March 16 in TheNew England Journal of Medicine, FDA officials warned the lack of evidence for unapproved stem cell treatments is ''worrisome." The officials cited reports of serious side effects, including two people who became legally blind after receiving the treatment in their eyes for macular degeneration.

In another case, a patient who received stem cell injections after a stroke developed paralysis and needed radiation treatment.

The FDA also notes that stem cell treatments potentially have other safety concerns, such as causing tumors to grow. And because patients may receive the treatments outside of formal research studies, it can be difficult to track their side effects.

Doctors say that treating the knee has less of a chance for complications. It is also the body part with perhaps the most research.

Still, even doctors who offer the treatment for arthritic knees say more study is needed.

"We don't have a lot of controlled trials yet," says Keith Bjork, MD, an orthopedist in Amarillo, TX, who has given stem cell treatments to about 500 patients with knee arthritis in the past 5 years. "Their results are the strongest evidence," he says.

The most common side effects are joint stiffness and pain at the injection site as well as swelling, according to the results of one study.

Where's the Research?

For knee injections, doctors often take stem cells from the patient's bone marrow, fat tissue, or blood. Doctors who do the treatments cite anecdotal evidence as validation that the treatments work.

Marc Darrow, MD, the Los Angeles physical medicine specialist who cares for Chung, says he has done thousands of stem cell treatments. He uses stem cells from the patient's own bone marrow, a process he says is simple and fast.

His patients’ pain often subsides after knee injections, he says. He also has had cases in which the ''before'' and ''after'' X-rays suggest an increase in cartilage, he says.

Harvey E. Smith, MD, an assistant professor of orthopedic surgery at the Hospital of the University of Pennsylvania, says it’s clear the treatment has an effect. What is not as clear is how it lessens pain. Researchers are studying whether the stem cells themselves cut inflammation or if they release substances that affect other cells. They also are looking at whether the treatments can regenerate worn-out cartilage.

Published studies have produced mixed results. One from 2014 showed that stem cell injections given after surgery to remove torn knee cartilage showed evidence of cartilage regeneration and lessened pain. In March, researchers who reviewed the findings of six studies on stem cells for knee arthritis found that patients reported good results with no serious side effects. More data is needed, however, before researchers can recommend it. 

''There is still not enough evidence to suggest this should be routine treatment for knee early osteoarthritis," says Wellington Hsu, MD, the Clifford C. Raisbeck professor of orthopedic surgery at Northwestern University Feinberg School of Medicine. Even so, he says, ''there is very little damage you are going to do with an injection to the knee. I think stem cells appear to be safe in orthopedic applications."

There is, of course, the risk that an investment of a couple thousand dollars will do nothing. But Hsu says that ''you are not going to find the catastrophic cases that will shut down a clinic [as may occur for other body parts].''

Consumer Caveats

For people who have knee arthritis, the most invasive treatment is total knee replacement, Hsu says. Doctors are also testing other injectable therapies, including platelet-rich plasma, hyaluronic acid, and steroids, he says.

Consumers who decide to try stem cell treatments for achy knees should research their doctor and the specifics on the stem cell treatment. It's crucial to ask the clinic where the stem cells come from, Smith says. Ask if they will retrieve them from your own bone marrow or fat tissue, or if they will come from donors. The FDA requires donor cells and tissues to be tested for communicable diseases. There is no consensus on which source is best, but most doctors use stem cells from fat, Hsu says.

The FDA suggests patients who decide to get stem cells for any purpose should speak to their doctor about the potential risks and benefits, and ask whether they are part of an FDA-approved clinical trial. Most often, doctors who offer stem cell treatments are orthopedists, plastic surgeons, or physical medicine and rehabilitation doctors,

The reduction in pain, however, isn’t permanent, Smith says. "The effect may last 6 months," he says, citing results from knee studies. When people are paying out of pocket, he adds, they may over-report good effects to feel like they got their money's worth.

Chung, the skier-cyclist, says the investment has been worth it. He plans to continue his injections once or twice a year, as needed, so he can stay active on the bike and the slopes.

Show Sources


Wellington Hsu, MD, Clifford C. Raisbeck professor of orthopedic surgery, Feinberg Northwestern University School of Medicine, Chicago.

Harvey E. Smith, MD, assistant professor of orthopedic surgery, University of Pennsylvania, Philadelphia.

Keith Bjork, MD, orthopedic surgeon, Amarillo, TX; clinical advisory staff member, Amnio Technology.

Julian Cameron, MD, orthopedic surgeon, Tamarac, FL.

Marc Darrow, MD, Los Angeles physical medicine specialist.

George Chung, stem cell recipient, Los Angeles.

CDC: "Osteoarthritis Fact Sheet."

The Journal of Bone and Joint Surgery: "Adult Human Mesenchymal Stem Cells Delivered via Intra-Articular Injection to the Knee Following Partial Medial Meniscectomy."

The New England Journal of Medicine: "Clarifying Stem-Cell Therapy's Benefits and Risks."

American Academy of Orthopaedic Surgeons annual meeting, presentation: ''Platelet-Rich Plasma, Bone Morphogenetic Protein, and Stem Cells: What Surgeons Need to Know." March 14, 2017, San Diego.

International Society for Stem Cell Research. "Stem Cell Facts."

Andrea Fischer, FDA spokeswoman.

FDA: "Consumer Information on Stem Cells."

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