Stem cell therapy for knees.

The procedure

One outpatient visit. If the cells are your own, they are taken first from belly fat or the back of the hip bone, and people who describe that harvest mostly call it the most painful part of the day.^[3] The injection itself is quick. In the largest trial the needle was guided by ultrasound.^[2]

How many sessions

Almost every trial gave one injection per knee.^[1] Some clinics sell repeat courses or add an IV drip on the day; ask what each extra is meant to do.

When it works, and how long it lasts

Most patients who reported back noticed a difference at two to four months. Some waited most of a year, and a few felt worse for six weeks or more before it settled.^[3]

Placebo-controlled trials measured the benefit for up to six months.^[1] One trial that followed people for longer found it lasted about three years, then drifted back towards where they started by year five.^[4]

Who it suits, and who it doesn't

Almost every trial studied mild to moderate osteoarthritis.^[1] The studies that split results by severity found milder knees did better than bone-on-bone knees,^[5] and a higher body weight predicted failure.^[6]

Risks

A sore, stiff or swollen knee for days to weeks is common. Donor cord products caused short-term swelling most often in trials.^[7] Joint infection is rare, but in reported cases outside trials every infected patient needed surgery.^[8]

Will insurance pay for it?

Usually not. The American Academy of Orthopaedic Surgeons says many of these treatments may not be covered, even approved ones,^[16] and the Arthritis Foundation says off-label use usually means no cover.^[17]

Is it better than PRP?

In head-to-head trials neither came out ahead,^[18] and patients report PRP costing about a third as much.^[3] PRP vs stem cells