Before You Pay for a Knee Injection, Read the Trials

Somewhere around 45, many active people discover that a knee, shoulder or heel has stopped cooperating. The traditional options were rest, anti-inflammatory pills, a cortisone shot and, eventually, surgery. Over the past decade, a new category has filled the space in between. It goes by names like regenerative medicine, orthobiologics and joint restoration, and it includes shockwave therapy, platelet-rich plasma and a range of cell-based injections.

The marketing tends to treat these as a single breakthrough. The evidence treats them very differently.

Start with the boring winner

Before looking at anything new, it is worth knowing what the best supported treatment is for the most common joint problem in midlife, knee osteoarthritis. It is exercise.

A Cochrane review¹ pooling more than 50 randomized trials found high-quality evidence that land-based therapeutic exercise reduces knee pain and improves physical function, with benefits comparable in size to those of common pain medications. Strengthening the quadriceps and hip muscles changes how load moves through the joint. It is also the foundation every other treatment depends on. An injection that calms pain for a few months is most valuable when it makes it possible to do the rehab that produces lasting change.

An injection that calms pain for a few months is most valuable when it makes it possible to do the rehab that produces lasting change.

Shockwave therapy

Extracorporeal shockwave therapy, often shortened to ESWT, delivers acoustic pressure waves through the skin to injured tissue. The proposed mechanisms include stimulating blood vessel growth and a healing response in chronically irritated tendons. Treatments are done in a clinic, usually over several sessions, and do not require needles or anesthesia.

The best studied uses are tendon problems, particularly chronic plantar fasciitis in the heel, calcific tendinopathy in the shoulder and some cases of tennis elbow and Achilles pain. Results across trials have been mixed but include several positive studies, especially for cases that have not responded to standard care. The UK's National Institute for Health and Care Excellence³ reviewed ESWT for stubborn plantar fasciitis and found no major safety concerns, but judged the evidence on how well it works to be inconsistent, so it advised using it with careful consent and outcome tracking.

For knee osteoarthritis specifically, the evidence for shockwave therapy is earlier and less consistent. A reasonable way to view ESWT is as a low-risk option for stubborn tendon pain, usually paired with a loading program, rather than a cure for arthritis.

Platelet-rich plasma

Platelet-rich plasma, or PRP, is made by drawing a patient's blood, concentrating the platelets in a centrifuge and injecting the result into an injured area. Platelets carry growth factors, and the theory is that concentrating them encourages repair.

The idea is appealing and the risk is low, but the knee data has been sobering. The RESTORE trial, published in JAMA² in 2021, randomly assigned 288 adults with knee osteoarthritis to three PRP injections or three saline injections. After 12 months, there was no significant difference in knee pain or in the volume of cartilage measured on MRI.

Other trials have reported more favorable results, and PRP preparations vary a lot from one system to another, which makes studies hard to compare. Some evidence is more encouraging for certain tendon problems. Still, anyone considering PRP for arthritis should know that the strongest single trial did not show a benefit over placebo, and that PRP is generally not covered by insurance.

Stem cell injections

This is the area where caution matters most. Many clinics advertise stem cell or exosome injections for joint pain, often derived from fat, bone marrow or birth tissue. The FDA has warned⁴ that most of these products have not been approved, that some clinics make claims that are not backed by evidence, and that patients have suffered serious harms, including infections and, in other uses, blindness.

Research on cell-based therapies for joints is ongoing and legitimate. Paying out of pocket for an unapproved product outside a clinical trial is a different thing.

How to think about your options

For most people with joint pain in midlife, a sensible sequence looks like this. Get an accurate diagnosis, since tendon pain, cartilage wear and referred pain from the back behave differently. Commit to a structured strengthening program, ideally guided by a physical therapist. Manage weight if it is a factor, since each pound of body weight adds several pounds of force across the knee during walking. Use targeted treatments such as shockwave therapy or injections as tools to make that program possible, chosen with a clear-eyed view of the evidence.

Ask any provider a few direct questions. What does the research show for my specific condition? What results should I expect, and by when? What does it cost, and is it covered? What happens if it does not work?

Joints respond to load, rest and patience. The goal is not a miracle injection. It is staying strong and moving, which is exactly what the research on muscle and aging says protects you most.