Cartilage Repair And Regeneration

Cartilage is the smooth lining on the surface of the bone that plays a role in joint lubrication and shock absorption. As we get older, the water content in cartilage decreases and other changes in it makes it vulnerable to injury, even knee ligament injuries. It can get worn out from traumatic sports injuries or a gradual “wear and tear” from years of impact loading of the joint.

Having a better understanding of the cartilage anatomy can help you take preventive measures and decide on treatment methods for your cartilage damage. Dr Kevin Lee has also done substantial research in cartilage repair using Arthroscopic Microfracture and Injections of Mesenchymal Stem Cells and Hyaluronic Acid to compare the safety and short term efficacy. For a more detailed understanding, you can read more about his novel, minimally invasive technique of cartilage repair and research on mesenchymal stem cells.

Patient Eligibility

cartilage repair

Image from

Articular cartilage in the knee damaged in a single, or focal, location.

Most candidates for articular cartilage regeneration are young adults with a single injury, or lesion. Older patients, or those with many lesions in one joint, are less likely to benefit from the surgery.

The knee is the most common area for cartilage restoration. Ankle and shoulder problems may also be treated.

Surgical Procedures for Cartilage Regeneration and Repair

Dr Kevin Lee uses different repair techniques depending on the :

  • Size and location of the lesion
  • Associated injuries
  • Age of patient
  • Whether it is a first or second-time operation

Some techniques use cells for repair while some do not. Cells refer to either cartilage cells or stem cells.

cartilage cells

Cartilage Cells
Stem cells are specialized cells that have the potential to become cartilage, bone, fat or muscle cells under the right circumstances. In Singapore, the use of stem cells for clinical cases is considered experimental and can only be done under a trial setting. Cartilage or stem cells are taken from the patient and are then cultured in the laboratory to increase their numbers. These cells are then seeded onto a scaffold which can then be implanted into the cartilage defect. So far, the mid-term results of using cartilage cells and the short-term results of using stem cells for cartilage repair seem promising. There is also plenty of research going on in an attempt to create the ideal scaffold for cartilage repair. Some scaffolds are used alone for implantation into defects while others work better with cells seeded onto them. The operation can either be done arthroscopically (keyhole) or via an open incision depending on the technique used and whether other problems in the joint, such as meniscal or ligament tears need to be addressed at the same time. In general, recovery from an arthroscopic procedure is quicker and less painful than traditional, open surgery. We will discuss the options with you and determine the right procedure that suits your needs. The most common procedures for cartilage restoration are:

  • Microfracture
  • Enhanced Microfracture or Autologous Matrix Induced Chondrogenesis (AMIC)
  • Autologous Chondrocyte Implantation (ACI or MACI)
  • Osteochondral Autograft Transplantation (OATS) or Mosaicplasty


Microfracture for Cartilage Repair

microfracture cartilage repair
  • This is one of the most popular cartilage repair techniques that can be done arthroscopically (keyhole) and as a day surgery procedure
  • The candidates are younger patients with single lesions that are not too large
  • It involves making small holes within the defect and the aim is to liberate small numbers of stem cells from the underlying bone marrow to repair the defect
  • To improve the results of this technique, we now augment it with post-operation injections of hyaluronic acid or platelet-rich plasma


Enhanced Microfracture Or Autologous Matrix Induced Chondrogenesis (AMIC)

  • This is a single-step procedure that can be done arthroscopically or via an open incision. This is Dr Lee’s preferred technique for treating lesions that are too large for treatment with microfracture.
  • This is an improvement on microfracture and it involves micro fracturing the defect (making small holes within the defect) first. Next, a membrane is used to cover the defect and held in place with special tissue glue or stitching. This membrane traps the stem cells and blood clot containing growth factors that were liberated during the microfracture procedure and acts as a scaffold for these cells to form new cartilage.
  • There are 2 membranes that can be used and they are Chondrogide (collagen membrane) and Hyalofast (a semi-synthetic derivative of hyaluronic acid, a naturally occurring extracellular matrix molecule and a major component of human cartilage). Here is a link to a video demonstrating this technique:
microfracture cartilage repair

Step 1- Microfracture The Defect


Autologous Chondrocyte Implantation (ACI) or Cartilage Transplantation

microfracture cartilage repair
  • 2-stage procedure
  • The 1st stage involves arthroscopic (keyhole) harvesting of chondrocytes (cartilage cells) from a non-weight-bearing area of the knee
  • The harvested cells are then grown in culture and multiplied
  • The 2nd stage takes place 3 weeks later when sufficient chondrocytes have been cultured
  • These are then implanted into the defect and there is no risk of rejection since the cells are the patient’s own
  • In the 1st generation technique, a patch of tissue is stitched over the defect and cultured cells are then injected underneath this patch which is then sealed up.
  • Current 3rd generation techniques (called MACI- matrix autologous chondrocyte implantation) do not require stitching of this patch as the cells are already grown onto the patch itself which is then fitted into the defect and held with special tissue glue
cartilage cells injection
Injection Of Cartilage Cells Under Periosteal Patch

ACI is most useful for younger patients who have single defects larger than 2 cm in diameter. ACI has the advantage of using the patient’s own cells, so there is no danger of a patient rejecting the tissue. It does have the disadvantage of being a two-stage procedure that requires an open incision. It also takes several weeks to complete.

Osteochondral Autograft Transplantation (OATS) or Mosaicplasty

cartilage transplant

During osteochondral autograft transplantation, cartilage is transferred from one part of the joint to another. Healthy cartilage tissue – a graft — is taken from an area of the bone that does not carry weight (non-weight bearing). The graft is taken as a cylindrical plug of cartilage and subchondral bone. It is then matched to the surface area of the defect and impacted into place. This leaves a smooth cartilage surface in the joint.

A single plug of cartilage may be taken or a procedure using multiple plugs, called mosaicplasty, may be performed.

Osteochondral autograft is used for smaller cartilage defects. This is because the healthy graft tissue can only be taken from a limited area of the same joint. It can be done with an arthroscope.

Mesenchymal Stem Cells in Cartilage Regeneration

Mesenchymal stem cells

Stem cells are specialised cells that have the potential to become bone, cartilage or fat forming cells under the right circumstances. Our medical director has been involved in the study of mesenchymal stem cells (from bone marrow) for both cartilage and bone repair since 2004. These are adult stem cells and we do not deal with embryonal stem cells in clinical practice currently.

Currently, the use of stem cells for use in human cartilage repair in Singapore is still classified as being experimental and must be done under the auspices of an ethical-board approved trial. This means that patients have to meet strict inclusion and exclusion criteria before they can be enrolled.

Dr Lee was the Principal Investigator of two grants using stem cells in cartilage repair: “A Phase One Multi-Center Study of a Novel, Minimally-Invasive Technique of Repairing Large Cartilage Lesions in the Human Knee” and “A Multi-Centre Randomised Controlled Trial Evaluating a Novel Minimally-Invasive Technique of Cartilage Repair in the Human Knee Using Autologous Mesenchymal Stem Cells and Hyaluronic Acid”. The first trial has been completed and the second trial aims to investigate the efficacy of microfracture combined with injections of mesenchymal stem cells.

In 2005, Dr Lee became the first orthopaedic surgeon to win both the Singapore Orthopaedic Association Young Investigator Award for his work on mesenchymal stem cells and cartilage repair in the knee and also the N Balachandran Award. In 2009, he mentored his trainee to win the Young Orthopaedic Investigator Award for an unprecedented second time.

For a comprehensive consultation to determine the most suitable type of treatment for your cartilage damage, contact us to make an appointment with our knee surgeon, Dr Kevin Lee at Singapore Pinnacle Orthopaedic Group.


Proper rehabilitation with the help of a trained physiotherapist is crucial to the success of the surgery. The rehabilitation protocols are individualised for each patient depending on the location of the repair, the technique used and associated injuries dealt with.

As healing progresses, your therapy will focus on strengthening the joint and the muscles that support it. It may be several months before you can safely return to sports activity.



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