Subchondral Bone Injection (Subchondroplasty)

A subchondroplasty is an injection of calcium phosphate bone-substitute material into a painful bone marrow lesion just beneath the cartilage, guided by live X-ray. It is for people — usually with knee pain — whose MRI shows a bone marrow lesion that matches their symptoms, whose arthritis is not yet severe, and whose knee is stable and well aligned^[2]. “Subchondroplasty” is a brand name; the generic term is subchondral bone injection.

A talus subchondroplasty is the same procedure performed in the talus, the ankle bone that sits beneath the shin bone, for a painful bone marrow lesion seen on MRI. It is used far less often than in the knee: in a 2021 systematic review, four of 17 studies involved the foot and ankle^[2]. Your physician will discuss whether the more limited evidence makes it reasonable for you.

It can be a way to put off knee replacement for some people, but it is not a substitute in advanced arthritis. In one meta-analysis, 22.4% of patients had a knee replacement within two years^[3]. It works best for a specific problem — a painful bone marrow lesion with mild to moderate arthritis. Other joint-preserving options include PRP, cortisone or gel injections and genicular nerve ablation.

Most people feel little during the procedure because it is done with sedation and local anesthetic, although pressure is common. Afterward, a deep ache in the bone and some swelling are common for several days and are usually managed with ice, elevation and pain relievers. Most people describe the recovery as much easier than knee surgery because there is no large incision.

Most people go home the same day and recover over several weeks. You may use crutches or limit weight on the leg for a short time, then gradually return to normal activities, often with physical therapy. In one meta-analysis, improvements in pain and function were seen as early as one month after the procedure^[3]. Desk work can often resume within days; jobs that involve heavy standing take longer.

Studies report meaningful pain relief for many patients, but the evidence is still early. One review found average pain fell from 7.8 to 3.4 out of 10^[2], and a 2026 meta-analysis found improvement lasting at least two years^[3]. Because most studies had no comparison group, it is not yet clear how much of that benefit comes from the procedure itself.

The most common problem is leakage of the calcium phosphate into the joint or surrounding tissue; one meta-analysis reported a median complication rate of 6.7%^[3]. Rare complications include bone infection and avascular necrosis^[2]. As with any procedure, there are small risks of bleeding, blood clots and reactions to sedation, and some people do not improve.

You will need a recent MRI showing the lesion and an evaluation of your knee alignment. Tell us about every blood thinner you take; we will coordinate with your prescribing doctor, and you should never stop one on your own^[7]. Follow any fasting instructions for sedation, arrange a ride home and have crutches ready if advised.

A cortisone or PRP injection goes into the joint space and acts on the joint lining and cartilage. A subchondral injection goes into the bone beneath the cartilage to fill and support a bone marrow lesion. The two approaches treat different sources of pain and can be used together as part of a plan. See PRP for knee arthritis for comparison.

Coverage varies and is often limited. The procedure is reported with a temporary CPT code for emerging technology^[8], and many plans consider it investigational because the research is still mostly uncontrolled^[2]. Medicare decisions are made case by case, commercial plans usually require prior authorization if they cover it, and workers’ compensation and no-fault follow their own rules. Our staff will verify your benefits and explain any self-pay costs in advance.