A stem cell procedure uses the body’s own repair cells, or donor cells, to treat disease or regenerate damaged tissue. These procedures range widely, from bone marrow transplants that replace a diseased blood system to targeted injections that aim to heal a worn-out knee joint. The common thread is harvesting cells with the ability to develop into specialized tissue, then delivering them where the body needs repair.
How Stem Cells Work in the Body
Stem cells are unique because they can both renew themselves and transform into more specialized cell types. But their therapeutic value goes beyond simply becoming new tissue. When introduced to a damaged area, stem cells promote healing through several mechanisms at once: they suppress inflammation, prevent nearby cells from dying off, recruit the body’s own repair cells to the site, and stimulate the growth of new blood vessels to nourish recovering tissue.
One reason mesenchymal stem cells (the type most commonly used in orthopedic and regenerative procedures) are so useful is their ability to calm the immune system. They release chemical signals that dial down overactive immune responses, which makes them relevant not just for injuries but for autoimmune conditions where the body attacks its own tissues.
Conditions Treated With Stem Cell Procedures
The most established use of stem cell procedures is the hematopoietic stem cell transplant, sometimes called a bone marrow transplant. This treats blood cancers and serious blood disorders by replacing a patient’s damaged bone marrow with healthy stem cells that can rebuild the blood and immune system. Current European practice guidelines list more than a dozen blood cancers as candidates, including leukemia, lymphoma, multiple myeloma, and myelodysplastic syndromes.
Beyond cancer, hematopoietic transplants are used for severe aplastic anemia, sickle cell disease, and transfusion-dependent thalassemia. Children born with severe combined immunodeficiency or certain metabolic storage diseases may also receive transplants as potentially curative treatment. In recent years, the list has expanded to include autoimmune conditions like multiple sclerosis, systemic sclerosis, Crohn’s disease, lupus, and myasthenia gravis.
On the regenerative medicine side, stem cell injections are being used for joint conditions like knee osteoarthritis, though this application is less established. A meta-analysis of 35 studies covering nearly 2,400 patients found that stem cell treatment significantly improved knee pain and self-reported physical function. It also improved cartilage quality, though its effect on cartilage volume was small and not statistically significant. When researchers looked only at the most rigorous trials, the benefits were real but more modest.
Where Stem Cells Come From
The two most common sources for regenerative procedures are bone marrow and fat tissue. Each has trade-offs.
- Bone marrow: Stem cells harvested from bone marrow are better at developing into bone and cartilage. The downside is that only about 0.001 to 0.01% of harvested bone marrow cells are actually stem cells, and the aspiration procedure can be painful.
- Fat tissue: Adipose-derived stem cells are easier to collect in large numbers through a minimally invasive procedure. They proliferate faster in the lab and are better at generating fat tissue, but they’re less effective than bone marrow cells at forming bone or cartilage.
For blood cancers and immune disorders, the stem cells come from bone marrow, circulating blood (after medication pushes stem cells out of the marrow), or umbilical cord blood.
Autologous vs. Donor Cells
In an autologous procedure, you receive your own stem cells. They’re harvested, sometimes stored or processed, then returned to your body. Because the cells are yours, the risk of immune rejection is essentially zero. This is the standard approach for many blood cancers like multiple myeloma, where doctors collect your stem cells, administer high-dose chemotherapy to destroy cancer cells, then reinfuse your stored cells to rebuild the blood system.
In an allogeneic procedure, the cells come from a donor, typically a matched sibling or an unrelated person identified through a registry. The advantage is that donor immune cells can recognize and attack remaining cancer cells, a phenomenon called graft-versus-tumor effect. The significant downside is graft-versus-host disease, where the donor’s immune cells attack your healthy tissues. In studies of allogeneic transplants, moderate to severe acute graft-versus-host disease occurred in about 31% of patients, and chronic forms affected around 42%. This risk of complications makes allogeneic transplants a more serious undertaking with higher treatment-related mortality.
What Happens During the Procedure
The experience depends entirely on the type of procedure. For a regenerative injection using bone marrow concentrate, the process typically takes place in a single session. After numbing the harvest site (usually the back of the pelvis), the surgeon inserts a specialized needle about 3 centimeters past the outer layer of bone to reach the marrow cavity inside. Using a syringe, they draw out roughly 60 milliliters of marrow, rotating the needle periodically to access fresh pockets of cells.
That raw marrow goes into a centrifuge, which spins it down to concentrate the stem cells and growth factors into just 2 to 5 milliliters of fluid. This concentrate is then injected directly into the treatment site, whether that’s a knee joint, a tendon, or a surgical repair. The whole harvest-to-injection process happens in one visit.
A hematopoietic stem cell transplant for cancer is far more involved. It requires days of preparatory chemotherapy or radiation to destroy the existing bone marrow, followed by the infusion of stem cells through an IV line (similar to a blood transfusion), then weeks of close hospital monitoring while the new cells engraft and begin producing blood cells.
Recovery and Timeline
Recovery from a regenerative injection is relatively quick. You can expect mild pain and swelling at the injection site for 48 to 72 hours. Most people return to light activity within days, though full benefit from the treatment develops over weeks to months as the cells do their work.
Recovery from a full stem cell transplant for cancer is a different experience entirely. Memorial Sloan Kettering describes the recovery window as extending from discharge to one year or longer. Immune system recovery alone typically takes 3 to 12 months. Most people feel noticeably stronger week by week, with hair regrowth and a return to more normal energy levels around the three-month mark. The earliest most patients return to work or school is 2 to 4 months after transplant, but the first year generally remains a period of ongoing recovery.
Risks and Side Effects
For regenerative injections, the most common side effects are mild: post-procedure pain, temporary swelling, and soreness at the harvest or injection site, usually resolving within a few days. Fever occurs in a meaningful percentage of patients receiving stem cell infusions, ranging from about 10% to over 20% depending on the condition being treated and the cell source.
More serious but rarer risks include infection at the injection site, blood clots, and tissue scarring (fibrosis). In a large multicenter study of over 2,300 patients who received autologous stem cell injections for joint disease, most adverse events were just post-procedure pain. However, 7 cases of tumors were identified, representing 0.3% of the study population. Three patients who received fat-derived stem cells for macular degeneration experienced vision loss. These serious events are uncommon but underscore why the source, processing, and delivery of stem cells matter.
For transplants treating cancer, the risk profile is substantially higher. Beyond graft-versus-host disease in allogeneic transplants, patients face prolonged immune suppression that leaves them vulnerable to infections for months.
Cost and Insurance Coverage
Stem cell procedures range from roughly $300 to $12,000, depending on the type and complexity. Medicare covers FDA-approved stem cell transplants, specifically hematopoietic transplants for blood cancers and bleeding disorders. If you’re admitted as an inpatient, Part A covers the hospital stay. For outpatient procedures, Part B applies, and after meeting your deductible, you pay 20% of the Medicare-approved amount. Medicare Advantage plans cover the same treatments and may offer additional benefits.
What Medicare and most insurers do not cover are regenerative stem cell injections for conditions like knee osteoarthritis, back pain, or joint injuries. These treatments lack FDA approval for those specific uses, so they’re considered experimental. If you’re considering a regenerative injection, expect to pay out of pocket.