Knee Cartilage Repair Surgery – Brisbane & Hamilton

What is Knee Cartilage Repair Surgery?

The ends of the bones inside the knee are covered by a smooth layer of articular cartilage.

Healthy articular cartilage provides a low-friction surface that allows the knee to move smoothly while distributing forces across the joint.

Unfortunately, articular cartilage has a relatively limited ability to heal following injury.

A focal cartilage defect is a localised area where this cartilage has been damaged or lost. This is different from the widespread cartilage loss that occurs throughout the knee in advanced osteoarthritis.

Cartilage injuries can occur following:

• sporting or twisting injuries
• direct impact to the knee
• patellar dislocation
• osteochondritis dissecans
• ACL or other ligament injuries
• meniscus injuries
• previous knee surgery
• injuries involving the bone beneath the cartilage

Sometimes there is no obvious single injury.

Not every cartilage defect causes symptoms and an abnormality on an MRI scan does not automatically require cartilage surgery.

When a focal cartilage lesion is believed to be responsible for persistent symptoms, several different cartilage repair or restoration techniques can be considered.

These include:

• microfracture and other marrow-stimulation procedures
• osteochondral autograft transfer (OAT)
• autologous minced cartilage procedures

These procedures work in different ways and are suitable for different cartilage lesions.

A systematic review of randomised trials comparing surgical treatments for knee cartilage defects concluded that there was insufficient evidence to recommend one cartilage procedure for every defect.

The aim is therefore not to choose a favourite cartilage operation, but to match the treatment to the individual cartilage lesion and patient.

Why is Knee Cartilage Repair Surgery Done?

A focal cartilage injury can cause:

• pain with activity
• recurrent swelling
• catching or mechanical symptoms
• difficulty running or playing sport
• reduced tolerance of loading through the knee

However, cartilage defects are not always responsible for knee pain.

Before recommending surgery, it is important to assess the whole knee, including:

• the size and location of the cartilage lesion
• depth of cartilage damage
• condition of the underlying bone
• knee alignment
• meniscus function
• ACL and other ligament stability
• patellar tracking
• cartilage elsewhere in the knee

Many patients can initially be treated without surgery using physiotherapy, strength training, activity modification, weight management where appropriate and other non-operative treatments.

Cartilage repair surgery may be considered when there is a symptomatic focal cartilage defect that remains troublesome despite appropriate non-operative treatment.

Cartilage restoration procedures are generally more appropriate for focal defects than for widespread osteoarthritis.

How is Knee Cartilage Repair Surgery Performed?

The operation depends on the characteristics of the cartilage injury.

Many cartilage procedures begin with an arthroscopy, or keyhole examination of the knee.

A small camera allows the cartilage lesion to be assessed directly, including its:

• size
• depth
• location
• stability
• surrounding cartilage
• underlying bone

The remainder of the knee can also be assessed for meniscus, ligament or other cartilage injuries.

Several different cartilage repair techniques may then be considered.

Microfracture Surgery

Microfracture is a marrow-stimulation procedure.

Small openings are created through the subchondral bone at the base of the cartilage lesion, allowing blood and bone-marrow elements to enter the defect.

A clot forms within the cartilage defect containing cells and biological factors originating from the underlying bone marrow.

Over time, this can develop into repair tissue.

The tissue formed following microfracture is predominantly fibrocartilage, which is biologically and mechanically different from the normal hyaline cartilage covering the knee.

Microfracture should therefore not be described as simply “regrowing normal cartilage.”

When is microfracture considered?

Microfracture has traditionally been used particularly for smaller, contained, full-thickness cartilage defects.

Patient and lesion selection are important.

A systematic review involving 3,122 patients treated with knee microfracture found improvement in knee function during the first two years, but the durability of this improvement was variable and long-term evidence was limited.

More recent evidence has reinforced the importance of lesion size. A 2024 systematic review examining microfracture for medium and larger knee cartilage defects at ten years or longer found declining clinical outcomes and relatively low return-to-sport rates for defects approximately 2–4 cm² in size.

Microfracture therefore remains a useful technique in appropriately selected cartilage lesions, but is not necessarily the best treatment for every defect.

Osteochondral Autograft Transfer – OAT/OAT

Osteochondral autograft transfer uses the patient's own cartilage and underlying bone to reconstruct a cartilage defect.

It is sometimes referred to as OAT, OAT or mosaicplasty.

“Osteochondral” means that the graft contains both:

• healthy articular cartilage, and
• the supporting bone beneath it.

“Autograft” means that the tissue comes from the patient's own knee.

How is osteochondral autograft transfer performed?

One or more cylindrical plugs of healthy cartilage and bone are harvested from a relatively low-load area of the knee.

The damaged cartilage and underlying bone are prepared to receive the graft.

The osteochondral plug is then inserted into the defect so that its cartilage surface sits level with the surrounding cartilage.

For larger defects, several plugs may sometimes be used.

Unlike microfracture, OAT transfers mature hyaline cartilage into the defect rather than relying on the formation of fibrocartilage repair tissue.

When is OAT considered?

Osteochondral autograft transfer is particularly useful for selected small to medium-sized focal cartilage or osteochondral defects.

One limitation is that only a finite amount of healthy cartilage can safely be harvested from elsewhere in the patient's knee.

Harvesting the graft also creates a defect at the donor site.

For these reasons, OAT becomes less attractive as the cartilage defect becomes very large.

A meta-analysis of prospective studies comparing osteochondral autograft transfer with microfracture found lower failure rates and better activity outcomes following OAT at mid-term follow-up. In the included studies, failure occurred in approximately 11% following OAT compared with 32% following microfracture.

A more recent network meta-analysis of randomised trials comparing microfracture, osteochondral autograft transplantation, autologous chondrocyte implantation and other cartilage techniques again demonstrated that outcomes vary according to technique and follow-up, reinforcing the importance of matching the procedure to the lesion.

These results should not be interpreted as meaning OAT is automatically better than microfracture for every patient. The procedures are often most appropriate for different lesion characteristics.

Autologous Minced Cartilage Implantation

A newer option is autologous minced cartilage implantation.

Like OAT, it uses the patient's own cartilage, but it uses that tissue in a very different way.

How does minced cartilage implantation work?

During the operation, small pieces of the patient's own articular cartilage are collected.

This cartilage can include suitable cartilage obtained from the edge of the defect or another appropriate area.

The cartilage is then minced into very small fragments.

These fragments contain the patient's own living chondrocytes.

The minced cartilage is placed across the prepared cartilage defect and secured within it, typically using biological components such as fibrin.

Unlike ACI or matrix-assisted ACI, the cells do not need to be sent to a laboratory and cultured for several weeks.

This makes minced cartilage repair a single-stage procedure.

What is the idea behind minced cartilage repair?

The small cartilage fragments provide multiple areas from which viable chondrocytes can migrate and contribute to new cartilage repair tissue.

The technique attempts to use the biological potential of the patient's own cartilage while avoiding the separate laboratory cell-expansion stage required for conventional ACI or matrix-assisted ACI.

An overview of autologous minced cartilage implantation describes the biological rationale and development of this single-stage cartilage restoration technique.

What does the evidence show for minced cartilage implantation and minced cartilage?

The evidence for minced cartilage repair is promising but still relatively early compared with established techniques such as microfracture, OAT and ACI/MACI.

A systematic review and meta-analysis of minced cartilage procedures identified three clinical studies involving 52 patients and 63 cartilage lesions. Patient-reported outcomes improved at 12 and 24 months, but the authors emphasised the relatively small amount of available clinical evidence.

Longer follow-up is now beginning to become available.

A 2023 study examining autologous minced cartilage repair at a minimum five-year follow-up reported improved pain and knee function in 28 available patients, with a mean cartilage defect size of approximately 3.5 cm².

More specifically for the minced cartilage implantation technique, a 2026 prospective study of arthroscopic minced cartilage implantation treatment reported clinical improvement at two years, although the study included only a small number of patients and did not contain a randomised comparison with an established cartilage procedure.

A 2026 controlled clinical study comparing an minced cartilage implantation minced-cartilage technique with MACI also reported encouraging two-year results in patients with large cartilage defects. However, the study involved only 20 patients.

minced cartilage implantation is therefore an interesting single-stage cartilage restoration technique, but the evidence is still developing. Longer-term studies and larger randomised comparisons are needed before it can be said to be superior to established cartilage restoration procedures.

Which Cartilage Repair Procedure is Best?

There is no single best cartilage operation for every patient.

The appropriate treatment depends on factors including:

• size of the cartilage defect
• depth of the lesion
• location within the knee
• condition of the underlying bone
• stability of the surrounding cartilage
• patient age
• activity requirements
• previous cartilage surgery
• knee alignment
• meniscus function
• ligament stability

Broadly, a small focal defect may be suitable for a relatively simple marrow-stimulation technique.

A small or medium-sized osteochondral defect may be particularly suitable for osteochondral autograft transfer.

Autologous minced cartilage procedures such as minced cartilage implantation provide another single-stage option for selected defects.

However, these are not rigid rules.

A systematic review of randomised controlled trials of knee cartilage surgery concluded that no single surgical treatment could be recommended for all knee cartilage defects.

The objective is therefore to select the technique that best matches the individual cartilage lesion rather than use the same procedure for every patient.

Preparing for Knee Cartilage Repair Surgery in Brisbane

Rehabilitation before surgery

Where possible, I encourage patients to maintain:

• full knee extension
• good knee movement
• quadriceps strength
• hip and lower-limb strength
• normal walking
• general cardiovascular fitness

The amount of exercise possible will depend on symptoms and any associated knee injuries.

Health preparation

Before surgery:

• stop smoking or vaping if possible
• maintain good nutrition
• optimise diabetes and other medical conditions
• maintain a healthy weight where appropriate
• provide a complete list of medications and supplements
• tell us about previous blood clots or anaesthetic problems
• arrange physiotherapy for postoperative rehabilitation

Preparing your home

Many cartilage procedures require a period of restricted weight-bearing, so you may require crutches following surgery.

Arrange help with shopping, meals and transport if required and remove obvious trip hazards from your home.

Because Brisbane has a warm and humid climate, particularly during summer, consider making sure you have access to a cool, comfortable and preferably air-conditioned environment during early recovery. Apart from making recovery more comfortable, a large meta-analysis found an association between warmer weather and higher rates of surgical-site infection. Keeping yourself comfortable and your surgical dressings clean and dry is therefore particularly important during Brisbane's warmer months.

What to Expect After Knee Cartilage Repair Surgery

Recovery varies substantially depending on the procedure performed.

Rehabilitation following a small microfracture procedure may be quite different from rehabilitation following an OAT, MACI or minced cartilage implantation procedure.

First 2 weeks

Early priorities generally include:

• controlling pain and swelling
• protecting the cartilage repair
• restoring appropriate knee movement
• activating the quadriceps
• avoiding unnecessary stiffness
• using crutches as instructed

2–6 weeks

Depending on the location and type of repair, weight-bearing may remain restricted during part of this period.

Physiotherapy may include:

• progressive knee movement
• quadriceps activation
• hip and core strengthening
• swelling control
• gradual progression of weight-bearing

6 weeks–3 months

As healing progresses, rehabilitation increasingly focuses on:

• normalising walking
• progressive strengthening
• balance and proprioception
• cycling and low-impact cardiovascular exercise
• restoring normal movement patterns

Progression should reflect the biology of the particular cartilage procedure, rather than simply the number of weeks since surgery.

3–12 months

Running, jumping and pivoting produce much greater loads across the repaired cartilage and are therefore introduced progressively.

Larger cartilage restoration procedures can require a relatively long rehabilitation period.

Return to sport should consider:

• symptoms
• strength
• movement control
• size and location of the cartilage repair
• associated surgery
• the demands of the particular sport

Long-Term Outcomes After Knee Cartilage Repair

The outcome of cartilage surgery depends substantially on the original lesion and the procedure performed.

Does cartilage repair regrow normal cartilage?

Not all cartilage procedures create the same type of tissue.

Microfracture predominantly produces fibrocartilage.

OAT transfers mature articular cartilage and its supporting bone from another part of the patient's knee.

minced cartilage implantation and other minced cartilage techniques redistribute small fragments of the patient's own articular cartilage containing viable chondrocytes across the defect.

This distinction is important when discussing “cartilage repair.” These operations do not all achieve the same biological result.

Does cartilage repair prevent arthritis?

This remains uncertain.

A focal cartilage injury can be part of a larger injury to the knee involving the meniscus, ligaments, underlying bone or other cartilage surfaces.

Cartilage repair surgery should therefore not be presented as a proven way of preventing future osteoarthritis.

Its primary objective is to treat a symptomatic focal cartilage or osteochondral defect.

When cartilage loss has become widespread throughout the knee, treatment may need to focus on the arthritis rather than attempting to repair an individual cartilage defect.

Things to Look Out for After Knee Cartilage Repair Surgery

Contact our office, your GP, physiotherapist, or seek urgent medical attention if you develop:

Possible infection

• increasing redness or warmth around the wounds
• increasing pain after initially improving
• persistent wound leakage
• pus or unusual discharge
• fever, chills or feeling significantly unwell

Possible blood clot

Seek medical attention for:

• new calf pain or tenderness
• significant one-sided leg swelling
• sudden shortness of breath
• chest pain or coughing blood

Sudden breathing symptoms require emergency assessment.

Increasing stiffness

Some stiffness is expected during early recovery.

Progressive loss of movement, particularly difficulty regaining full knee extension, should be discussed with your treating team.

Persistent or recurrent swelling

Some swelling is normal during rehabilitation.

Repeated substantial swelling as activity increases may indicate that the knee is being loaded beyond its current capacity.

New injury

A significant twist, fall or unexpected impact during the healing period can potentially damage the cartilage repair.

A sudden increase in pain, swelling, catching or loss of function following another injury should be assessed.

Knee Cartilage Repair Surgery

Dr Alexey Borshch is a specialist orthopaedic surgeon in Brisbane with a particular clinical focus on surgery of the knee, hip, ankle and lower limb.

His practice as a Brisbane knee surgeon includes the assessment and treatment of focal cartilage injuries, meniscus tears, ACL injuries, patellar instability and other sporting and traumatic conditions of the knee.

When surgery is appropriate, treatment may range from arthroscopic procedures and microfracture or marrow stimulation through to osteochondral grafting for larger or deeper defects. The procedure is selected according to the characteristics of the individual cartilage injury rather than using the same technique for every patient.

Dr. Borshch completed his medical degree at the University of Queensland before undertaking specialist orthopaedic training in Queensland. He completed the Australian Orthopaedic Association training program and the Royal Australasian College of Surgeons Fellowship Examination in Orthopaedic Surgery. He obtained specialist registration in Orthopaedic Surgery in 2022 and is a Fellow of the Australian Orthopaedic Association.

He offers consultations in Hamilton, Brisbane, and conducts private orthopaedic surgery at Brisbane Private Hospital.