Topic 10 · Treatment options

Stem Cell & Regenerative Therapies (Emerging)

Eleven human studies, all non-randomised, and in nine of them the cells were given during an operation — so the cells cannot be separated from the surgery. The insurer calls it investigational.

DGOU 2024 Position

→ Experimental treatments using stem cells (from fat, bone marrow, etc.) to regenerate cartilage. Stem cells are "blank" cells that can become cartilage cells. Exosomes are tiny healing signal packets cells release.

The German Society of Orthopedics and Traumatology considers adipose-derived MSC therapy for OLT experimental [92]:

→ Adipose-derived = from fat tissue; MSC = Mesenchymal Stem Cells (cells that can become cartilage)

Recent Case Studies (2025)

A November 2025 case using heparin-conjugated fibrin hydrogel with MSCs [93]:

→ Hydrogel = gel-like scaffold that holds cells in place; fibrin = natural clotting protein

Exosome Therapy (Pre-Clinical)

Exosomes are emerging as potential therapy for cartilage repair [94]:

CBMA (Concentrated Bone Marrow Aspirate)

CBMA is a simpler stem cell approach harvested during surgery [1]:

→ CBMA = liquid from inside your bones (rich in stem cells) concentrated and applied to the defect

The whole evidence base was mapped in July 2026 — and it is eleven studies

→ Someone finally counted every human study of cell therapy for this exact condition. The count is eleven, and in nine of them the cells were given during an operation — so you cannot tell whether the cells helped or the surgery did.

A systematic scoping review charted every human clinical study applying cell-based therapy to post-traumatic ankle osteoarthritis or OLT [229]. It covers BMAC, bone marrow-derived cell transplantation, adipose-derived MSCs, stromal vascular fraction, micro-fragmented adipose tissue, and peripheral blood products — effectively everything on this card.

The review also argues explicitly that ankle osteoarthritis is a different disease from knee osteoarthritis — predominantly post-traumatic, younger and more active patients, arising from focal talar lesions rather than diffuse degeneration — and that knee evidence should not be read across to it.

Even “which cells” is still an open question

→ Clinics sell “stem cells” as though it were one product. It is not — the cells vary by tissue source and by which subpopulation gets selected, and the field has not settled which is best.

A July 2026 animal study injected human fat-pad-derived mesenchymal stromal cells into a rat osteoarthritis model, comparing cells sorted for the marker CD271 — a marker associated with greater regenerative potential — against ordinary unsorted cells [243]. Both cell groups clearly beat saline on cartilage degeneration, inflammatory cytokines, and pain-related neuropeptides. But the CD271-selected cells outperformed unselected cells on one measure at one timepoint only — histology at day 14 — with no difference in the macroscopic cartilage score, the inflammatory markers, or the pain markers. This is a two-week rat study and it is not evidence for or against any human treatment. It earns a line here for one reason: it shows that the field is still arguing about the basic composition of the injection, which sits awkwardly beside marketing that presents a settled product.

Added August 8, 2026 — the knee now has a 24-trial meta-analysis, which mostly measures how far ahead of the ankle it is

A meta-analysis published August 7 pooled 24 randomized trials, 1,389 patients, of MSC therapy for cartilage defects — significant improvements in pain (SMD −1.31), function, and cartilage volume, with adverse events no different from control [406]. Every included trial is knee — the inclusion criteria say so explicitly — so the scoping review's ankle count above (eleven studies, zero randomized) is untouched, and the review's own warning against reading knee evidence across to the ankle applies to this paper in full. Two subgroup findings are still worth a line, because they bear on which cell product anyone should ever accept: autologous cells beat allogeneic (SMD −1.88 vs −0.80), and bone-marrow-derived beat adipose-derived on cartilage volume. Both point toward the same product — the patient's own marrow — that the BMAC-augmentation trials on topic 30 used, and away from the off-the-shelf allogeneic and fat-derived products most heavily marketed to patients.

Added September 4, 2026 — the standalone-marrow-cell rung gains its first long-horizon controlled dataset, from the field’s own pioneer, with the commercial flag attached

→ For years the honest summary here was: cells injected without surgery, into an arthritic ankle, rest on a single case report. A new 88-patient, 15-year study just replaced that — and both its strength and its salesmanship need stating.

Philippe Hernigou — the surgeon who built the marrow-cell literature in hip osteonecrosis — together with the Regenexx group published a contralateral-controlled series of 88 patients with ankle osteoarthritis in both ankles, treated 2000–2014: the more painful ankle received intraosseous bone marrow concentrate — injected into the bone beneath the joint surface, not into the joint space — while the other ankle got usual non-operative care [458]. The endpoint was not a pain score but the hard one this site cares about: did the ankle end in fusion or replacement? Over 15 years, 18.2% of treated ankles reached that endpoint versus 50.0% of the untreated opposite ankles (adjusted HR 0.24), with treated ankles accumulating on average 3.5 more procedure-free years — and in an exploratory analysis, more delivered CFU-F cells meant longer survival (HR 0.70 per 10,000 cells), the first dose-response signal in ankle marrow-cell work.

What it does not show. Not randomized; the treated ankle was chosen because it was worse, and the authors say plainly the findings “do not establish a causal treatment effect.” The cohort is non-traumatic ankle OA — a different disease from the post-traumatic, OLT-driven arthritis this site tracks, and this page has itself argued against reading evidence across disease types. And the author list is the Regenexx orbit — the company that sells cash-pay marrow procedures in the US — so this is simultaneously the best standalone-injection data the ankle has ever had and a marketing asset for the clinics most likely to quote it. Two details survive the discounting and matter for any future conversation about biologics: the route was intraosseous (subchondral), not the intra-articular injection most clinics actually sell, and the dose-response finding gives the first reason to ask any provider “how many CFU-F do you deliver, and do you count them?”

Added September 11, 2026 — the lesion-size cutoff gets called what it is: an administrative number, not a biological one

→ Korea’s health system allows marrow-concentrate (BMAC) treatment for cartilage defects only when the lesion is bigger than 2 cm² — but most talus lesions are smaller than that. Korean foot-and-ankle surgeons went back through the paperwork and found the 2 cm² line was never tested against outcomes: it is a leftover from a 2011 filing, built on numbers that were originally invented to predict when microfracture fails — a different procedure entirely.

A committee of the Korean Foot and Ankle Society published a reassessment of the national coverage rule for BMAC in cartilage defects [471]. Korea approved BMAC in 2011 only for lesions of 2–10 cm² in patients under 50, on four low-level reports — and neither that notice nor the 2018 reassessment ever compared outcomes below versus above the line. The paper’s most transferable finding is about where such numbers come from: the lesion-size cutoffs circulating in OLT care were derived as prognostic factors for bone marrow stimulation — the size at which microfracture starts to fail — and were never established as efficacy thresholds for any other treatment, leaving an untested gray zone between 1.5 cm² and 2.0 cm². BMAC series have reported improvement in lesions far below the line (mean 103 mm² in one series it cites).

Why this earns a section on a page about an insurer that calls cell therapy investigational: this page’s own CBMA bullet above repeats a “>1.5 cm²” recommendation, and the scoping review [229] warned against reading knee evidence across to the ankle — this paper documents a national payer doing exactly that, with the threshold frozen into regulation. It is a policy review, Korea-specific, written by authors who want the rule loosened, and it contains no new patient data — but it is the clearest statement yet on this site that the size numbers that gatekeep biologic treatment of OLT are administrative history, not measured biology. For a large-lesion, post-allograft ankle like this one, the practical lesson is the same one in the other direction: when a coverage rule cites a size threshold, ask what procedure that number was derived from before accepting that it applies.

Added September 25, 2026 — what surgeons actually do while the evidence stays flat: the first AOFAS-wide practice survey

→ Everything above keeps reaching the same verdict: for the ankle, cell-therapy and biologic evidence is thin to absent. A new survey of 129 American foot-and-ankle surgeons shows how little that constrains the operating room — nine in ten use at least one biologic, and two-thirds of the marrow-concentrate users put it into cartilage procedures like the ones this site tracks.

A survey of American Orthopaedic Foot & Ankle Society members — authored from the Hospital for Special Surgery and Cedars-Sinai — asked 129 responding surgeons what orthobiologics they use, where, and why [489]. 92.2% use at least one orthobiologic. BMAC — bone marrow aspirate concentrate, the product behind the augmentation trials on topic 30 and the Hernigou series above — is the most used (73.9% of users), and osteochondral procedures are among its leading indications (65.9%), second only to revision fusion. The survey’s own framing is the honest one: with the evidence “heterogeneous,” use “is often determined by individual surgeon preference.” Two details are worth keeping. First, the generational split: surgeons in their first decade of practice use BMAC at 80.4% versus 51.3% for those past twenty years (adjusted P=.010) — the practice is being adopted fastest by the surgeons trained most recently, on the same unimproved evidence base. Second, the mirror image: of the ten respondents who use no orthobiologics at all, seven cited lack of evidence and five cited cost — the same two walls this site has documented from the payer side, in the international consensus that found no product superior to another [216] and in an insurer that classes these products as investigational.

What this changes on this page: nothing about efficacy — it is a Level IV cross-sectional survey of reported behavior, with the authors’ own caveat that surgeons who use orthobiologics were likelier to answer, and it contains no outcomes. What it adds is the denominator. When a consult proposes “we’ll add BMAC” to a cartilage procedure, that proposal is now measurably normal practice for a US foot-and-ankle surgeon — and normal practice that the field’s own survey attributes to preference rather than data. The practical question this page has already derived from [458] survives unchanged: ask what is being injected, by what route, and whether anyone counts the cells.

Status: These therapies remain experimental. There are still no large RCTs for ankle OLT, and as of July 2026 the standalone injection — the form most often marketed directly to patients — rests on two studies in focal repair and a single case report in degenerative post-traumatic ankle OA; as of September 2026 the non-traumatic degenerative form additionally has the 88-patient contralateral series above [458], with its non-randomized design and commercial authorship stated. This converges with the 2026 international orthobiologics consensus, which found no formulation or preparation method superior to another [216], and with the AAOS ankle osteoarthritis guideline, which found no reliable evidence for stem cell therapy [228]. Three independent methods reaching the same place is the meaningful signal. None of this establishes that cell therapy fails — it establishes that the study capable of showing whether it works has not been done.