Why the Ankle and Achilles Are Studied Together
Tendon tissue has limited healing capacity, so researchers have asked whether cells can help it repair.[1] A 2019 review of tendon regeneration describes the idea that mesenchymal stem cells from bone marrow or fat might improve tendon healing. The review draws that support from in vitro and in vivo studies, and notes that the exact mechanisms are not yet fully understood.[1]
For a plain-language introduction to the cells themselves, read what stem cells are and what mesenchymal stem cells are on the GIOSTAR blog.
Achilles Tendon Studies
Human evidence for tendon disorders includes systematic reviews.[2][3] A 2021 systematic review and meta-analysis in Annals of Rehabilitation Medicine pooled four prospective clinical studies of mesenchymal stem cells in tendon disorders. It found improvements in pain, function, imaging and arthroscopic findings, with a pooled effect size of 1.87, and a meta-regression that linked higher cell doses to greater pain relief. The authors said larger studies are needed.[2]
A 2022 systematic review in the Journal of Experimental Orthopaedics covered 22 clinical studies with 658 patients, across rotator cuff, elbow, patellar, Achilles and gluteal tendons. Almost all of the studies reported no serious side effects during follow-up. All but one used the patient's own cells, and one used allogeneic adipose-derived cells.[3]
The Achilles studies themselves are small.[4][13] A first-in-human phase IIa study enrolled 10 patients with mid-portion Achilles tendon pain and injected autologous bone marrow-derived mesenchymal stem cells. At 24 weeks no serious adverse reactions were observed, and pain and symptom scores improved from baseline. The report describes a single group of patients, so it can speak to safety and early signals, not to how much the cells added to the healing.[4]
A registered phase 1 and 2 study of RCT-01 in chronic Achilles tendinosis compared injections with placebo injections. Its registry entry lists 8 people enrolled and a status of terminated, so the registry offers no result to weigh.[13]
Ankle Studies
Ankle studies fall into two groups: cells given on their own into the joint, and cells given during a surgical repair of the talus.[5][8]
Adipose tissue studies in the ankle are small.[5][7] A prospective, non-randomized study treated 31 patients with ankle osteoarthritis by injecting micro-fragmented adipose tissue. Scores improved at 6, 12 and 24 months, but scores worsened significantly between 12 and 24 months. No severe complications were recorded.[5] Micro-fragmented adipose tissue is an autologous tissue preparation.[5]
One systematic review pooled cell therapies used to augment surgery for talar chondral defects, covering 477 procedures. At a mean follow-up of 34.8 months, the visual analogue pain score improved by 4.4 points out of 10, and the American Orthopaedic Foot and Ankle Score improved by 31.1 points out of 100. The reported reoperation rate was 0.06%, and few articles reported data on complications.[6]
A 2024 systematic review of adipose-derived stem cells in ankle conditions included eight studies. It found clinical improvement in patients with osteochondral lesions and ankle osteoarthritis and no serious complications. All studies performed a concomitant procedure, and the authors described the evidence as scarce and low quality.[7]
A 2026 systematic scoping review of cell-based therapies for post-traumatic ankle osteoarthritis and talar lesions charted 11 clinical studies. In nine of the 11, the cells were given with a concomitant operation, so the cells' own contribution could not be separated from the operation. The authors described the signals as promising but preliminary.[8]
Registered trials in this area include the following. The phase 3 CARTISTEM study, a donor umbilical cord blood product, was added to microfracture surgery in 102 patients with talar lesions and is listed as completed.[9] A randomized, double-blind phase 3 study of allogeneic stem cells added to arthroscopic treatment of talar lesions planned 70 patients, and its status is listed as unknown.[10] An earlier early-phase study of the same umbilical cord blood product, with 28 patients, is registered with its status also listed as unknown.[11] A phase 1 study of autologous mesenchymal stem cells in ankle osteoarthritis enrolled 6 patients, and its title names side effects as the focus.[12]
How to Read an Ankle or Achilles Study
A few details tell you much about any study in this area:
- Where the cells went. Into the Achilles tendon, into the ankle joint, or into the talus during a repair. A surgery that happens at the same time changes what the cells can be credited with.[8]
- The comparison. Whether the study had a control group, and what that group received.
- The size. Ten patients in one Achilles study[4] and 477 procedures pooled in one review[6] are different kinds of evidence, and the reviews note how few studies there are.[7]
- The follow-up. Compare how long each study followed patients. The reports above range from 24 weeks in one trial[4] to a mean of 34.8 months in one review.[6]
Where to Find These Studies
Registered studies are listed publicly on ClinicalTrials.gov. Published results are on PubMed. Every source in this guide is listed under References with its PubMed, DOI and registry links.
The companion guide stem cell research and the knee covers that joint on its own. For the general service, see stem cell therapy at GIOSTAR.
Further reading: the FDA's consumer page on regenerative medicine therapies, fda.gov (a regulator page; not a numbered reference).
Regulatory Status
Stem cell clinics and stem cell use are arguably subject to FDA oversight, and a 2026 review of biologics regulation says that oversight has been enforced unevenly.[14] Our stem cell therapy is not approved by the FDA.
