Nanofat (also called nanofat grafting) is a mechanically processed form of a patient’s own fat used as an intra-articular injection for osteoarthritis (OA), most commonly of the knee. It is an orthobiologic intended to reduce inflammation and pain and potentially support cartilage, rather than a proven disease-modifying or first-line treatment.

What it is and how it is prepared

Fat is harvested by liposuction (often from the abdomen), then emulsified by passing it repeatedly between syringes and through fine filters. This produces a liquid emulsion of very small particles that can be injected through a thin needle. The product is rich in stromal vascular fraction cells (including adipose-derived stem/stromal cells, pericytes, and endothelial progenitors), extracellular matrix fragments, growth factors, cytokines, and other paracrine signals. Intact adipocytes are largely disrupted compared with coarser “microfat.” Preparation is typically done point-of-care without enzymatic digestion or cell culture.

Proposed mechanism in OA

Effects appear mainly paracrine rather than from long-term cell engraftment. Preclinical work (in vitro chondrocyte/synoviocyte studies and rat OA models) shows reduced pain-related and pro-inflammatory mediators, increased anti-inflammatory factors such as TGF-β, support for chondrocyte anabolic markers (e.g., collagen type II, aggrecan), and reduced catabolic enzymes. Some studies report effects comparable to cultured adipose-derived stem cells. Clinical MRI in small series has shown possible reductions in bone-marrow edema and joint effusion plus modest cartilage/meniscus appearance changes, but these findings are preliminary.

Clinical evidence

Small clinical series and two recent systematic reviews (including one from 2025) report consistent short- to medium-term improvements in pain (VAS) and function (WOMAC or similar scores) after a single intra-articular injection, often within weeks to months and lasting many months in responders. One retrospective series of 18 knee OA patients used ~6 mL concentrated nanofat per joint and noted score improvements plus no major adverse events; a few patients had follow-up MRI suggesting structural benefit. Local reactions (transient pain or swelling at the injection site) are the most common side effects and usually resolve in days to weeks. Serious or systemic events appear rare in published reports.

Limitations are important: studies are mostly small, uncontrolled or poorly controlled, heterogeneous in processing and patient selection, and lack long-term follow-up or large randomized trials versus placebo, hyaluronic acid, PRP, or microfragmented fat. Standardized protocols and cost-effectiveness data are lacking. Reviews therefore describe nanofat as promising but still investigational.

Practical considerations

It is typically considered for mild-to-moderate symptomatic knee OA that has not responded adequately to weight loss, physical therapy, activity modification, and simpler injections. It is sometimes combined with hyaluronic acid or SVF. Results vary by OA severity, alignment, and patient factors. Regulatory status differs by country; in many places it is offered as a minimally manipulated autologous tissue product rather than an approved drug or cell therapy.

This is not a substitute for established conservative care or, when indicated, surgical options. Discuss risks (including those of liposuction), expected benefits, alternatives, and evidence quality with an orthopedic or sports-medicine specialist experienced in orthobiologics. Larger trials are still needed before it can be considered standard.