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Cartilage Repair and Transplantation (ACI, OATS)


What is an articular cartilage defect in the knee?

Articular cartilage is the shiny, white surface that covers the ends of most bones and protects them during movement by allowing the joint surfaces to glide smoothly with less friction. An articular cartilage defect (also known as a chondral injury) may occur as the result of a traumatic injury or simply wear-and-tear over time. Chondral defects are graded from mild to severe:

  • Grade 1 – The cartilage becomes soft in the earliest form of damage
  • Grades 2 and 3 – As the condition worsens, the cartilage may develop a shredded appearance. The grade of injury depends on the size and thickness of the defect
  • Grade 4 – The cartilage may wear away completely, leaving the underlying bone exposed.


How do I know if I need surgery? 

In certain cases, non-operative treatment may be beneficial for patients whose MRI shows only mild softening of the cartilage surface without any large defects. However, if severe chondral injuries are left untreated, it can eventually hinder your ability to move free from pain and cause irreversible joint damage. In cases like these, Dr. Potts utilizes the most advanced surgical techniques for cartilage repair in order to provide his patients with the best results possible.


What types of surgery are available for articular cartilage injuries?

In the past decade, there have been many exciting advances in the surgical treatment of articular cartilage defects. The most commonly used treatment used to involve simply smoothing the rough areas of the defect with a shaving technique. However, years of research in this area has led to the development of several new ways to address this difficult problem. The most commonly performed procedures for treating chondral defects include:

  • Shaving or Debridement
    • This technique performed during knee arthroscopy has been popular for decades, and is a common treatment for patients with a cartilage injury that has not worn all the way down to the bone (especially under the kneecap). Using special arthroscopic instruments, shredded or frayed articular cartilage is smoothed and shaved down. Ideally, this treatment decreases friction and irritation, swelling, and pain – but it does not cure the cartilage defect.
  • Microfracture
    • During an arthroscopic procedure, the base of the damaged area is scraped to create a bleeding bed of bone, and then small holes are created in the subchondral bone to allow healing cells to flow into the defect and stimulate fibrocartilage formation. Research has shown that this tissue is a hybrid cartilage. Although this newly grown cartilage is durable and can function for many years, it may not have the same durability or strength as the original hyaline cartilage that existed before the injury.
  • Autologous Chondrocyte Implantation (ACI)
    • This is a two-step procedure where articular cartilage is biopsied from the patient’s knee during the initial arthroscopy and sent to a lab where the chondrocytes (cartilage cells) are processed and grown. After a growth period of around 1 month, the cells are then re-implanted into the cartilage defect under a special patch to facilitate healing.
  • Osteochondral Allograft Transfer (OATS)
    • If a cartilage defect is too large for an autograft, an allograft is usually considered. The allograft is fresh cartilage and bone from a donor, and can be shaped to fit the exact contour of the defect and then fit into place. Allografts are typically done through an open incision, and available instruments can create grafts between 10 and 35 mm in diameter.
    • First, the defect is exposed and sized. A guide pin is then placed through the center of the lesion, and depth measurements are taken from the prepared recipient site. The allograft plug is then removed from the donor tissue, and recipient depth measurements are marked on the plug. Excess bone is removed from the graft to match the patient’s measurements, and then the graft is inserted to fill the defect.