If you are weighing up options for a cartilage defect, one of the most useful questions is whether you are comparing like with like. ChondroFiller is a CE-marked collagen scaffold that can be delivered in two different ways depending on the size and location of the defect and the clinical picture: as a non-surgical outpatient injection, or as the core scaffold within the Liquid Cartilage surgical protocol. Traditional techniques such as microfracture and autologous chondrocyte implantation (ACI) are both surgical procedures. Understanding these categories clearly helps set realistic expectations.

What ChondroFiller Is

ChondroFiller is a type I collagen hydrogel scaffold — a Class III CE-marked medical device made from cell-free collagen. When placed into a cartilage defect, it self-gels in approximately three to five minutes, forming a porous three-dimensional matrix. The patient's own progenitor cells then migrate into the scaffold and, over time, begin to remodel it towards cartilage-like tissue. ChondroFiller does not contain hyaluronic acid and is not a steroid or a pain-blocking agent; it is a biologic scaffold intended to support tissue repair.

The CE Class III marking and the published clinical evidence for the device belong to ChondroFiller itself. It can be delivered either non-surgically (by ultrasound-guided injection in an outpatient setting) or surgically (as the scaffold in a keyhole procedure).

Two Pathways Using ChondroFiller

The ChondroFiller Injection — Non-Surgical Pathway

For smaller, accessible defects and smaller joints such as the hand, wrist or ankle, ChondroFiller can be administered as an ultrasound-guided outpatient injection without a general anaesthetic or theatre time. The injection is placed precisely into the defect under ultrasound guidance. Recovery is straightforward; most patients return to normal activities promptly. This pathway suits patients for whom surgery would be disproportionate to the defect, or those who prefer to avoid theatre.

Liquid Cartilage — The Surgical Protocol

Liquid Cartilage is not a product. It is the Lee Liquid Cartilage Protocol (LLC Protocol) — a keyhole (arthroscopic) surgical technique developed by Professor Paul Y. F. Lee. It uses ChondroFiller as the principal scaffold, but combines it with biological adjuncts and a structured peri-operative approach to engineer the best possible conditions for cartilage regeneration.

The surgical steps include arthroscopic preparation of the defect (creating a stable rim and removing calcified cartilage), a switch to dry CO2 insufflation so the scaffold can gel correctly, optional application of autologous mesenchymal stem cells (from bone-marrow aspirate concentrate or micro-fragmented adipose tissue) for larger or more challenging defects, injection of ChondroFiller under dry conditions, and a final intra-articular flood of platelet-rich plasma and tranexamic acid once the scaffold has set. Early neuromuscular activation with electrical muscle stimulation begins from day zero, and a structured rehabilitation programme follows over several months.

Liquid Cartilage is genuine surgery — it takes place in theatre under anaesthetic and carries a recovery period including protected weight-bearing for the first few weeks. It is suited to larger or load-bearing defects in the knee, hip, shoulder and ankle. It is not an injection.

Traditional Surgical Options

Microfracture

Microfracture remains a widely used first-line surgical treatment for small cartilage defects. The surgeon makes small holes in the underlying bone to release marrow cells, which form a blood clot in the defect. The tissue that forms is fibrocartilage — mechanically inferior to native hyaline cartilage. Published evidence indicates that microfracture can give good short-term symptom relief, but clinical benefit often declines after two to five years, and reoperation rates are substantial. The technique also involves deliberate disruption of the subchondral bone plate, which may affect future treatment options.

Autologous Chondrocyte Implantation (ACI and MACI)

ACI and its matrix-assisted variant MACI use the patient's own cartilage cells, grown in a laboratory, for reimplantation. The process requires two surgical stages: an initial biopsy to harvest cells, then a second procedure (often open rather than keyhole) to implant the cultured cells. Published series report durable outcomes in appropriately selected patients, with IKDC functional improvements broadly comparable to those seen with ChondroFiller-based approaches. However, the two-stage process is lengthy and expensive, carries risks at the biopsy site, and requires an extended rehabilitation of twelve months or more. Graft hypertrophy has been reported in a meaningful proportion of ACI cases.

Osteochondral Grafting

Techniques such as osteochondral autograft transfer (mosaicplasty) and osteochondral allograft transplantation move bone-and-cartilage plugs from a donor site (patient's own joint or a donor) into the defect. These are well-established for larger osteochondral lesions. Autograft procedures create a secondary donor-site defect; allograft carries a small risk of disease transmission and depends on tissue availability. Both are primarily surgical options with their own recovery requirements.

How the Approaches Compare

The table below summarises the key distinctions at a glance.

• ChondroFiller injection: non-surgical, outpatient, ultrasound-guided, suitable for smaller or accessible defects, prompt recovery.
• Liquid Cartilage (LLC Protocol): keyhole surgery, single stage, uses ChondroFiller scaffold with biologics and optional MSCs, suited to larger or load-bearing defects, structured recovery over months.
• Microfracture: surgical, single stage, produces fibrocartilage, benefit may decline after 2–5 years, disrupts subchondral bone.
• ACI/MACI: surgical, two stages, uses the patient's own cultured cells, durable in selected patients but lengthy and costly process.
• Osteochondral grafting: surgical, indicated for larger osteochondral lesions, carries donor-site considerations.

In published clinical data, ChondroFiller used within the LLC Protocol has shown IKDC functional improvement of approximately 30 points over 12 to 36 months in knee defects — comparable to results reported for ACI in similar cohorts — while achieving this in a single minimally invasive stage without the need for cell culture or a biopsy harvest. Evidence suggests the tissue formed is hyaline-like rather than the fibrocartilage typical of microfracture. Long-term durability data beyond five years continue to accumulate.

Recovery

Recovery differs markedly across these approaches. The ChondroFiller injection requires no theatre, no anaesthetic, and most patients resume normal activities promptly with minimal restriction. The Liquid Cartilage surgical pathway requires protected weight-bearing for approximately four to six weeks, a graduated physiotherapy programme extending to several months, and a full return-to-sport timeline of around four to twelve months depending on the joint and defect. Microfracture typically restricts weight-bearing for six to eight weeks with sport delayed for several months. ACI involves a similarly extended or longer rehabilitation.

Choosing the Right Approach

Which pathway is appropriate depends on several factors: the size and depth of the defect, the joint involved, the patient's activity level and goals, whether the joint is well aligned, and whether previous treatments have been tried. A detailed assessment — including imaging and clinical examination — is needed before any recommendation can be made. The choice between the ChondroFiller injection and the Liquid Cartilage surgical protocol is not simply a question of preference; it reflects clinical suitability for each pathway.

None of the approaches described here should be presented as a cure or guaranteed reversal of arthritis. Each is a joint-preservation intervention; benefits vary between individuals and should be discussed with a specialist.

References

Corain M, Zanotti F, Giardini M, Gasperotti L, Invernizzi E, Biasi V, Lavagnolo U. The use of an acellular collagen matrix ChondroFiller Liquid for trapeziometacarpal osteoarthritis. Cartilage. 2023.

Mithoefer K, Williams RJ, Warren RF, Potter HG, Spock CR, Jones EC. The microfracture technique for the treatment of articular cartilage lesions in the knee. J Bone Joint Surg. 2005;87(9):1911–20.

Peterson L, Minas T, Brittberg M, Nilsson A, Sjögren-Jansson E, Lindahl A. Two- to 9-year outcome after autologous chondrocyte transplantation of the knee. Clin Orthop Relat Res. 2000;374:212–34.

Next Steps

The London Cartilage Clinic at Harley Street offers specialist assessment for patients considering cartilage repair, including evaluation for both the ChondroFiller injection and the Liquid Cartilage surgical protocol. If you would like to understand which pathway may suit your situation, a consultation with Professor Lee or the wider team can help clarify your options.