Accessibility Tools

What is Knee Cartilage?

Healthy cartilage is a white smooth material that covers the ends of the bones at the joints. It serves as a protective cushion, allowing smooth, almose frictionless movement of the joints as one bone end moves on the other. It also provides shock absorption at the joints.

Causes of Cartilage Wear

The articular cartilage in the knee can wear away as part of the normal ageing process.

Articular cartilage wear can be accelerated by injury and other factors, leading to premature osteoarthritis.

Symptoms of Cartilage Wear

If the cartilage gets damaged by disease, wear and tear or injury, the tissues around the joint become inflamed, causing:

  • Pain
  • Swelling
  • Stiffness
  • Locking
  • Limited movement
  • Bony deformity

Cartilage Damage Diagnosis

Cartilage damage in the knee can be assessed clinically and with imaging tests.

To assess your knee I will:

  • Take a medical history
  • Perform a physical examination
  • Assess the joint's range of motion
  • Organise imaging tests

Imaging tests:

X-rays will show a reduction in joint space in cases of significant cartilage wear. They will also show bony spurs (osteophytes), knee angulation and deformity, and show up any loose bony bodies in the knee. X-Rays are an important tool in the planning for knee joint replacement.

MRI scans can create detailed images of both hard and soft tissues within your knee. An MRI can produce cross-sectional images of internal structures and are very accurate in the assessment and diagnosis of cartilage, ligament and meniscal injuries or damage.

Who Is Suitable for Cartilage Surgery?

Most candidates for cartilage repair are young adults with a single injury, or lesion. The size and location of the lesion and the status of other knee structures will help determine whether surgery is possible for you.

To improve the chance of success additional procedures could be recommended, these could include:

  • Knee realignment (osteotomy) and
  • Ligament reconstructions

Older patients, or those with many lesions in one joint, are less likely to benefit from the surgery, as this process is more representative of osteoarthritis.

Treatments for Osteoarthritis

There is no known cure for osteoarthritis, however there are several treatments and lifestyle modifications that can help you ease your pain and symptoms.

The objective of the treatment is to reduce pain, improve joint movement, and prevent further damage to joint.

The treatment of osteoarthritis involves:

  • Medications – including anti-inflammatory drugs, steroid injections, and artificial joint fluid injections (Hyaluronic acid or HA)
  • Lifestyle modifications
  • Low impact exercise program

Cartilage Procedures

The most common procedures for damaged cartilage are:

  • Chondroplasty
  • Microfracture or nano-fracture procedure
  • Marrowstim stem cell procedure
  • Matrix-Induced Autologous Chondrocyte Implantation (MACI)
  • Osteochondral Autograft Transplantation
  • Autologous adipose derived stem cell transplantation


This procedure involves

  • Smoothing the roughened areas
  • Removing any loose fragments

In many cases, patients who have joint injuries, such as meniscal or ligament tears, will also have cartilage damage.

This involves smoothing out any unstable areas of cartilage by using fine mechanical shavers and thermal devices.

Benefits of chondroplasty are that it is not invasive with quick recovery, but it does not stimulate cartilage regeneration.

Microfracture and nano-fracture

The goal of microfracture is to stimulate the growth of fibrocartilage by creating a new blood supply. As with chondroplasty this procedure involves

  • Smoothing the roughened areas
  • Removing any loose fragments and
  • Treating exposed bone to stimulate cartilage recovery.

A special tool is used to make multiple tiny holes in the exposed cortical bone of the joint surface to promote a healing response. Stem cells from the underlying bone marrow migrate into the area to create new fibrocartilage tissue.

This procedure may be combined with a Marrowstim stem cell procedure (see below).

This procedure is best for young patients with

  • A single lesion
  • Lesions under 2cm
  • Healthy subchondral bone

The recovery is usually slower than a chondroplasty as specific rehabilitation protocols are required to allow the new fibrocartilage to regenerate.

Marrowstim stem cell procedure

In this procedure bone marrow is taken from the top of the tibia and treated in a centrifuge to concentrate the stem cells which are injected back into the knee at the end of the operation. The Marrowstim procedure can easily be done at the same time as arthroscopy of the knee.

Matrix-Induced Autologous Chondrocyte Implantation (MACI)

MACI is a three-step procedure.

  • Healthy cartilage tissue containing living chondrocytes is removed arthroscopically
  • Cartilage cells are sent to the laboratory and grown in vitro
  • The new cells are then implanted back into the patient’s knee

The culturing process takes six weeks.

The benefits of this approach are

  • No danger of tissue rejection
  • The implanted material may regenerate hyaline cartilage

This procedure is best for young patients with

  • A single lesion
  • Lesions under 2cm
  • Healthy subchondral bone

Treatment for a MACI procedure can be costly and the culturing is not covered by private health insurance.

Osteochondral Autograft Transplantation

Matchstick shaped cartilage and bone plugs are taken from non-critical areas in the knee and moved to fill in cartilage defects in critical weight-bearing areas in the knee. It is a single stage procedure and can be done arthroscopically or through a small incision. This procedure can be combined with a Marrowstim stem cell procedure

Outcomes of Cartilage Repair

Outcomes are variable and depend on the amount of cartilage damage that is present in the knee.

Typically, cartilage repair patients report

  • Significant improvement in symptoms
  • Ability to return to most activities, although certain impact activities may need to be minimiSed.

Cartilage Damage Prevention

The best way to keep your knee joint healthy is to

  • Keep a low body weight
  • Perform regular low impact exercises (bike riding, swimming, gym exercises)
  • Build core muscles by exercise or Pilates


Some patients find no improvement in their symptoms following cartilage repair surgery. The quality of the cartilage tissue that regenerates can vary among patients and affect the result of surgery.

Preparing for Knee Cartilage Surgery

Once it has been decided that surgery is required, preparation is necessary to achieve the best results and a quick problem free recovery.

Preparing mentally and physically for surgery is an important step toward a successful result.

  • A treatment plan will be created specifically tailored for you
  • I will need a complete list of your medications so that I can advise which ones should be stopped prior to surgery
  • The admitting hospital will advise you of the fasting time and your arrival time on the day before surgery
  • Do not eat or drink anything, including water, for 6 hours before surgery
  • Stop taking aspirin, warfarin, anti-inflammatory medications or drugs that increase the risk of bleeding one week before surgery
  • Stop or cut down smoking to reduce your surgery risks and improve your recovery

After Your Operation:

Your knee will be filled with long lasting local anaesthetic at the end of the operation so there should be very little pain after surgery. However you will be given a prescription for pain killers and possibly anti-inflammatory medications.

The wounds take 7-10 days to heal. Most patients improve dramatically in the first 2 weeks.

Occasionally, there are periods where the knee may become sore and then settle again. This is part of the normal healing process.

Full weight-bearing and walking is allowed immediately after arthroscopic surgery. Most patients do not need walking aids after arthroscopic surgery, but if you do need crutches, the hospital will supply them. Crutches can usually be discarded after a day or two in most cases.

When can I Drive After Cartilage Surgery?

Driving a car is discouraged for 48 hours after an anaesthetic. After 48 hours, your ability to drive will depend on the side you had your operation, left or right, and the type of vehicle you drive, manual or automatic. You can drive whenever you feel comfortable and are walking well with good control over your legs and reflexes. You should not drive under the influence of strong painkillers, e.g. Endone or codeine.

Return to Work After Cartilage Surgery

Return to work will vary depending on the procedure performed and type of work you do. Most patients can return to office work within a few days. Labour intensive work however, may require up to 3 weeks or longer before returning to full duties.

During this period you should try to avoid the following activities:

  • Prolonged standing,
  • Heavy lifting,
  • Bending or
  • Excessive stair climbing

Return to Sport After Cartilage Surgery

Time to return to sport depends on the type of surgery and the state of the knee, among other factors.

You may increase your activity level within comfort limits, avoiding excessive pain and swelling.

In cases of significant cartilage damage you will be advised to reduce your impact activities, e.g. running, jumping etc.