Knee Cartilage Injury (Chondral & Osteochondral Defects) and Cartilage Repair in Bristol

Cartilage injuries are some of the most frustrating knee problems to live with. The smooth surface lining the joint gets damaged – sometimes from a single twist or impact, sometimes from years of overload – and because cartilage has almost no blood supply, it does not heal like other tissues. The result is activity-related pain, swelling after exercise, catching, and a knee that just does not feel right.

The good news is that cartilage treatment has advanced enormously. I work within one of the UK specialist cartilage treatment centres and offer the full range of cartilage restoration procedures – from chondroplasty and scaffold-based repairs (AMIC, Hyalofast) through to osteochondral grafting. ACI (Autologous Chondrocyte Implantation) is considered the gold-standard treatment for larger focal defects, but it is rarely available in practice – access is restricted to a small number of NHS specialist centres and is typically not offered by private hospitals. The right approach depends on the type of injury, its size and location, and whether there are contributing problems like malalignment, meniscus loss, or ligament instability.

What is knee cartilage?

Articular cartilage is the smooth, low-friction surface covering the ends of the bones where they form the knee joint. It helps the knee glide and spreads load across the joint. It is different from the meniscus, which is the shock-absorbing pad that sits between the femur and tibia.

Types of cartilage injury

Partial-thickness chondral injury

The surface cartilage is damaged but does not go all the way down to bone. It may look like softening, fissuring, fraying, or a shallow crater. These injuries can be painful and mechanically irritating, but the surgical options are different from deeper defects.

Full-thickness chondral defect

The damage extends through the entire cartilage layer, often exposing the underlying bone. This type of defect is more likely to cause persistent symptoms and is the main target for cartilage restoration procedures.

Osteochondral injury

Both the cartilage surface and the bone underneath are involved – for example after a twisting injury, an impact, or recurrent kneecap dislocations. These injuries sometimes require procedures that restore both the cartilage and the bone beneath it.

What causes cartilage damage?

Acute injury – a twist, impact, sports injury, or fall
Recurrent kneecap instability – each dislocation episode can shear cartilage off the patella or femoral groove
Meniscus injury or loss – reduces shock absorption and increases cartilage load
Ligament instability – especially ACL-related giving way that repeatedly stresses the joint surface
Malalignment – bow-leg or knock-knee overloading one compartment
Wear and tear – early osteoarthritis changes and progressive cartilage thinning

Symptoms

Cartilage injuries present in different ways, but the common pattern is:

Activity-related knee pain – especially stairs, squats, running, jumping, or pivoting
Recurrent swelling after activity
Catching, clicking, or a "rough" sensation in the joint
Brief locking or giving way (sometimes from loose fragments)
A general loss of confidence in the knee

When to seek urgent assessment

Seek urgent medical advice if you have:

A locked knee (cannot fully straighten)
Large swelling soon after injury
Inability to weight-bear
Suspected recurrent kneecap dislocation

How I assess cartilage injuries

Getting the treatment right depends on understanding two things: the defect itself, and what is going on in the rest of the knee. A cartilage repair done in a malaligned or unstable knee is likely to fail, so I always look at the bigger picture.

I use an MRI to map the defect – its size, depth, location, and whether the bone underneath is involved. I also check the meniscus and ligaments on the same scan. X-rays assess joint space, bone changes, and alignment. Sometimes the full extent of the injury only becomes clear during arthroscopy (keyhole surgery), which can also allow treatment at the same time.

The treatment spectrum

Cartilage procedures sit on a spectrum from simple to complex. The right option depends on defect depth, size, location, bone involvement, and what you need the knee to do.

Cartilage repair (smoothing and stabilisation)

Chondroplasty is the first-line procedure for many cartilage problems. I perform it arthroscopically – smoothing unstable or frayed cartilage, removing loose flaps, and reducing mechanical irritation. It can improve symptoms significantly, but it does not regrow normal hyaline cartilage. I often combine it with other work – for example, addressing cartilage damage found during an ACL reconstruction.

Cartilage regeneration (growing new tissue)

Regenerative techniques encourage the body to fill a defect with new tissue. These are considered for full-thickness defects where the cartilage is gone down to bone. The exact technique depends on the defect characteristics and the condition of the rest of the knee.

A note on microfracture: microfracture was once the most commonly used regenerative technique – drilling small holes in the bone to stimulate a healing response. However, the evidence no longer supports its use. The repair tissue it produces is fibrocartilage rather than true hyaline cartilage, and outcomes tend to deteriorate over time. I do not offer microfracture as a standalone procedure. Scaffold-based techniques like AMIC and Hyalofast have largely replaced it.

Cartilage reconstruction (replacing the damaged surface)

Reconstructive procedures replace damaged cartilage with new tissue or grafts, particularly for larger, deeper, or more complex defects.

Cartilage restoration options in detail

1) Chondroplasty

Most commonly used for partial-thickness injury or unstable cartilage flaps
Often combined with addressing the underlying cause – for example, ligament reconstruction or meniscal repair at the same time

2) OATS (Osteochondral Autograft Transfer)

OATS transfers one or more small plugs of healthy cartilage and bone from a non-weight-bearing area of your knee into the damaged area.

Best suited to focal full-thickness or osteochondral defects of the right size
Uses your own tissue (autograft), so no graft rejection risk
Some patients get donor-site soreness, which is the main trade-off

3) Scaffold-based cartilage repair (AMIC and Hyalofast)

Scaffold-based techniques have become the main regenerative option for cartilage defects. They use a collagen or hyaluronic acid membrane to provide a framework that guides new cartilage formation within the defect. Both are single-stage procedures – no separate cell-harvesting operation or laboratory cell culture is needed.

AMIC (Autologous Matrix-Induced Chondrogenesis) combines an abrasion chondroplasty with a collagen scaffold – such as Chondroguide – placed over the prepared defect. The scaffold protects the repair environment and guides tissue formation.

Hyalofast works on a similar principle but uses a hyaluronic acid-based scaffold instead of collagen, again combined with bone marrow stimulation.

Widely available – unlike ACI, which is rarely accessible in practice
Best suited to moderate-sized focal full-thickness defects where chondroplasty alone is not enough

For most patients with a cartilage defect that needs more than debridement, a scaffold-based repair is the most realistic regenerative option available.

4) ACI (Autologous Chondrocyte Implantation)

ACI uses your own cartilage cells (chondrocytes), grown in a laboratory, to regenerate cartilage tissue within a prepared defect. It is considered the gold-standard biological option for larger focal full-thickness defects – but in practice it is rarely available. Access is restricted to a small number of NHS specialist cartilage centres and is typically not offered by private hospitals.

Particularly valuable for larger full-thickness chondral defects where OATS would be too small
Requires a staged approach – first a keyhole procedure to harvest cells, then implantation once the cells have been cultured in the lab
Results are best when the "knee environment" is right – alignment, meniscus, and stability all need to be addressed

The limited availability of ACI is one of the main reasons scaffold-based alternatives like AMIC and Hyalofast have become increasingly important – they offer a practical single-stage option for patients who would benefit from more than chondroplasty alone.

5) OCA (Osteochondral Allograft)

OCA uses a transplanted donor graft that includes both cartilage and underlying bone. It is particularly useful when there is significant bone involvement beneath the cartilage defect.

Often the best option for osteochondral defects or larger defects where bone restoration is needed alongside cartilage
A single graft restores both the surface (cartilage) and structural support (bone)
Planning focuses on matching graft size and shape and ensuring the knee is well aligned and stable

Treating the whole knee, not just the defect

This is the part that makes the biggest difference to long-term results. A cartilage repair done in isolation – without addressing the reason the cartilage failed – is at risk of failing again. Depending on your knee, the plan may include:

Alignment correction (osteotomy) if one compartment is being overloaded
Meniscus preservation or restoration if the meniscus is damaged or missing
Ligament stabilisation (such as ACL reconstruction) if instability is contributing to cartilage damage
Patellofemoral optimisation if the kneecap joint is involved

I will discuss which combination of procedures, if any, best protects the repair and gives you the most durable result.

Recovery and rehabilitation

Rehabilitation is critical to getting a good result from cartilage surgery. Recovery depends on which procedure was performed and the size and location of the defect.

Typical recovery pattern (guide only)

Early phase: swelling control, restoring movement, protecting the repair
Strength and control phase: progressive strengthening of quadriceps, hamstrings, and hips, improving movement quality
Return-to-impact phase: gradual progression to running and sport-specific drills when safe

Procedures involving cartilage reconstruction (OATS, scaffold-based repairs, ACI, or OCA) need a more protective early phase and a structured return to impact. I plan each rehabilitation programme around the repair technique, your knee mechanics, and your goals.

Risks and limitations

All surgery carries risks. Specific cartilage procedure risks vary with technique, but may include:

Infection, blood clots, stiffness, or prolonged swelling
Ongoing pain or incomplete symptom improvement
Failure of the repair or need for further surgery
Donor-site discomfort (more relevant to OATS)
Graft-related issues (more relevant to OCA)
Cartilage wear progression elsewhere in the knee over time

I will cover the expected benefits, alternatives, rehabilitation course, and specific risks for your knee in clinic.

Frequently asked questions

What is the difference between a cartilage injury and a meniscus tear?

Articular cartilage is the smooth lining on the bone ends. The meniscus is a separate shock-absorbing structure that sits between the bones. Both can cause pain and swelling, and they often occur together – particularly after twisting injuries.

Can knee cartilage heal on its own?

Rarely. Cartilage has almost no blood supply, so its ability to repair itself is very limited. Some symptoms can improve with rehabilitation and load management, but deeper defects usually need targeted treatment if they remain limiting.

Do I need an MRI?

Yes – an MRI is essential for cartilage injuries. I need it to map the defect size, depth, and location, check whether the bone underneath is involved, and assess the meniscus and ligaments. Without it, I cannot plan treatment properly.

What about ACI?

ACI is considered the gold-standard biological option for larger focal cartilage defects, but it is rarely available in practice. Access is restricted to a small number of NHS specialist centres and is typically not offered by private hospitals. For most patients, scaffold-based techniques like AMIC and Hyalofast are the most practical regenerative option. Smaller defects may be better treated with chondroplasty or OATS, and defects with significant bone loss may need an osteochondral allograft. Getting the right procedure for the right defect is what matters most.

How long does recovery take after cartilage surgery?

It varies widely. A simple chondroplasty may recover relatively quickly. Scaffold-based repairs, OATS, ACI, and OCA typically require a longer, structured rehabilitation programme – often nine to twelve months before returning to impact activity.

Can I be assessed for cartilage treatment in Bristol?

Yes. I see patients at my Bristol clinics for cartilage assessment, including the full range of restoration procedures from arthroscopic chondroplasty and scaffold-based repairs through to osteochondral grafting.