Knee Cartilage Injury and Treatment
Knee cartilage overview
Cartilage is a rigid yet flexible connective tissue found in many areas of the body, including your joints. Articular cartilage coats areas of bone that are in close proximity to each other. It is found at the ends of your femur (thigh bone), tibia (leg bone) and on the underside of your patella (kneecap).
Articular cartilage is important because it provides a smooth surface for your bones to guide, acts as a shock absorber and protects bones from the pressure of your body weight. However, it does not have its own blood supply and must rely on the fluid in your joint (called synovial fluid) for its nutrients. Because of this, articular cartilage has limited ability to heal itself if damaged.
Knee cartilage injury
Cartilage injuries are common. In fact, more than half of people who undergo knee surgery for an unrelated injury are found to have cartilage injuries as well. Athletes who participate in twisting and pivoting sports such as football, soccer and basketball are particularly at risk. A cartilage injury can occur along with another knee injury, such as an anterior cruciate ligament (ACL) tear or it can occur on its own. Cartilage can also be injured from years of accumulated wear and tear. Symptoms of a cartilage tear may include pain, swelling, locking, catching and decreased range of motion.
Treatment of cartilage injury
There are a number of treatment approaches to cartilage injuries including nonsurgical, minimally invasive surgery (arthroscopy) and open surgery (arthrotomy). The approach your doctor recommends will depend on the size of your injury and your activity level. Nonsurgical treatment may include physical therapy, knee bracing, anti-inflammatory medication and injection into the joint with cortisone or hyaluronic acid.
Surgical options available at OHSU range from minimally invasive arthroscopic surgery to larger open surgeries to replace the damaged cartilage. The type of surgery recommended will depend on a number of factors including the size of your injury, your expectations and goals, the overall condition of your knee, and if there is any damage to the underlying bone.
If you have been given a diagnosis of osteoarthritis, cartilage repair surgery will likely not be recommended as this damage is often too extensive to be repaired. In other words, we are able to treat small potholes in the road, but if the whole road needs re-paving, knee replacement surgery may be a better option.
Common cartilage surgeries performed at OHSU
Two small incisions are made just below your kneecap and a thin fiber optic camera is inserted. This allows us to visualize the inside of the knee joint, then trim and smooth the damaged cartilage. Removing the damaged tissue allows for healthy cartilage to potentially fill in the defect.
Microfracture surgery is also done arthroscopically. First, the damaged cartilage is removed. Then, small holes are poked into the bone below, bringing new cells to the area which will eventually go on to grow new scar cartilage. Though this new type of cartilage is not quite as strong as your normal cartilage, it does serve to put a cover on the “pothole” which helps to improve many people’s symptoms.
Autologous chondrocyte implantation (ACI)
Another approach to cartilage repair involves replacing damaged cartilage with new cartilage that essentially matches the other cartilage in your knee.
ACI is a two-step procedure. In the first step, new cartilage cells are grown. During the second step, these new cartilage cells are implanted in your body.
First, healthy cartilage tissue is removed from a non-weight-bearing area of your bone. This step is done as an arthroscopic procedure. This tissue, which contains healthy cartilage cells, or chondrocytes, is then sent to the laboratory and the cells are cultured and increase in number over a three- to five-week period. During the second step, an open surgical procedure, or arthrotomy, is then done to implant the newly grown cells.
Neocart clinical trial
OHSU is one of a few hospitals around the country involved in the Neocart clinical trial, now in its third and final phase of investigation. This study seeks to compare microfracture surgery to a novel approach to cartilage restoration called Neocart. In this clinical trial, patients are randomly assigned to receive either microfracture surgery or Neocart. Neocart is a bio-engineered cartilage patch that is grown from your own cartilage cells.
First during an arthroscopic procedure, a small sample of cartilage is taken and sent to a lab to grow. The cartilage is grown over six to eight weeks in a matrix and arrives at OHSU as a patch that can be trimmed and customized to fit inside your knee through a small open incision.
DeNovo NT allograft cartilage transplant
Unlike ACI and Neocart, DeNovo surgery implants new cartilage that comes from a donor. There is no need for an arthroscopic procedure to harvest cartilage beforehand . Through a small incision “mini arthrotomy,” tiny new pieces of cartilage are adhered to your knee using a fibrin glue. Over time, these new pieces of cartilage will grow and fuse with your normal surrounding cartilage.
Osteochondral allograft transplantation
If a cartilage defect is too large for the above surgeries to be effective and/or if there is damage to the underlying bone, we may recommend use of donor cartilage and bone to replace your injured cartilage and bone. This is done through a small open incision in your knee. A thin piece of bone with the overlying cartilage attached is press-fit inside your knee. We work with an excellent tissue bank to ensure we have access to high-quality grafts screened for diseases and contamination.