Osteochondral Autograft Transplantation (OATS)

Why am I having this operation?

You have an area of damaged cartilage within your knee. Cartilage is the smooth, white tissue that covers the ends of the bones and allows the joint to move smoothly without pain.

Unlike many other tissues in the body, cartilage has a very limited ability to heal itself. When cartilage is damaged, it can cause pain, swelling, clicking, catching, and difficulty with sporting or everyday activities.

An OATS procedure (Osteochondral Autograft Transfer System) is designed to repair a localised area of cartilage damage by replacing it with healthy cartilage and bone taken from another part of your own knee.

The aim is to restore a smooth joint surface, reduce symptoms, and help protect the knee from further deterioration.

What exactly is an OATS procedure?

An OATS procedure involves transferring a small plug of healthy cartilage and underlying bone from a non-weight-bearing part of your knee into the damaged area.

Think of it as replacing a damaged patch of lawn with a healthy plug of turf from an area that is rarely used.

Because the graft contains both cartilage and bone, it provides immediate structural support and restores the joint surface with normal hyaline cartilage—the same cartilage you were born with.

Fig.1. Knee joint showing plugs taken from right side of image and transferred into the cartilage defect (Bottom Left of image)

Why has this procedure been recommended for me?

OATS surgery is most suitable for patients who have:

• A small to moderate-sized cartilage defect
• A well-defined area of damage
• Healthy surrounding cartilage
• Ongoing symptoms despite non-surgical treatment
• A desire to remain active

It is often recommended for younger and active patients who have sustained a cartilage injury through sport or trauma.

For larger cartilage defects, other cartilage restoration procedures may provide a better solution.

What happens during the operation?

The procedure is performed under a general anaesthetic.

Using either keyhole surgery or a small incision, the damaged cartilage area is identified.

A cylindrical plug of healthy cartilage and bone is then taken from a non-weight-bearing area of your knee.

The damaged area is carefully prepared and a matching socket is created.

The healthy graft is then inserted into the defect and gently press-fitted into place so that the cartilage surface sits flush with the surrounding joint surface.

The operation typically takes between 40-60 mins depending on the size and location of the defect.

Fig.2. Arthroscopic view showing unstable cartilage defect (arrowed) and 2 bone plugs inserted to stabilise the defect.

What are the benefits of OATS surgery?

The main advantages of OATS include:

• Restoration of normal joint cartilage
• Use of your own tissue
• No risk of graft rejection
• Immediate structural support from the transplanted bone
• Durable cartilage repair
• Improved knee function
• Reduction in pain and swelling

For appropriately selected patients, OATS can provide excellent long-term results.

What are the risks?

All surgery carries some risk.

Potential complications include:

• Infection
• Bleeding
• Blood clots (DVT or pulmonary embolism)
• Knee stiffness
• Numbness
• Ongoing pain or swelling
• Failure of graft healing
• Persistent cartilage symptoms
• Need for further surgery

Because the graft is taken from another part of your knee, some patients experience discomfort at the donor site. This is usually temporary and settles with time.

Your surgeon will discuss these risks with you before surgery.

What should I expect after surgery?

Recovery following cartilage restoration surgery requires patience.

The transplanted graft needs time to heal and integrate with the surrounding bone and cartilage.

First 6 weeks

You will usually require crutches and you will need to be non weight bearing for 6 weeks on the operated leg.

During this period the focus is on:

• Protecting the graft
• Reducing swelling
• Regaining knee movement
• Activating the quadriceps muscles

Physiotherapy

Physiotherapy is a critical part of recovery.

A structured rehabilitation program helps restore:

• Range of motion
• Strength
• Balance
• Proprioception
• Functional movement

Return to sport

Return to activity is gradual.

Typical milestones include:

Recovery timelines vary depending on the size and location of the cartilage defect and whether any additional procedures were performed.

Frequently asked questions

Will the graft be rejected?
No. The graft comes from your own knee, so there is no risk of rejection.

Will the donor site cause problems?
Most patients have little or no long-term symptoms from the donor site. The graft is taken from an area that does not normally bear significant weight.

How successful is OATS surgery?
When performed for the correct indication, OATS surgery has a high rate of successful cartilage healing and good long-term outcomes.

Will I get arthritis later?
Cartilage restoration procedures aim to improve symptoms and potentially slow the progression of arthritis. However, they cannot completely eliminate the future risk of degenerative joint changes.

Is OATS the right procedure for me?
Every cartilage injury is different.
The decision to proceed with OATS surgery depends on several factors, including:

• Your age
• Activity level
• Symptoms
• MRI findings
• Size and location of the defect
• Previous treatments

Dr. Gohil will discuss all available treatment options and help determine the most appropriate solution for your individual situation.