What is Articular Cartilage?
A joint in the human body is composed of the ends of two different bones gliding against one another to allow joint range of motion. Articular cartilage is the coating cartilage on the ends of the bones which allows for smooth, nearly frictionless, pain free joint range of motion. However, articular cartilage can be lost either as the result of a traumatic injury or as the result of wear and tear in the joint over time. This loss or wearing down of articular cartilage is called arthritis. A thin wear spot in articular cartilage is called a chondral defect. When articular cartilage wears completely away from the ends of the bones in a joint, then the result is “bone on bone” arthritis. Although a challenging problem, there are some promising surgical treatments to repair and replace areas of articular cartilage loss in a joint.
Dr. Cunningham is an articular cartilage surgeon at Vail Summit Orthopedics and Neurosurgery. He is an expert at diagnosing and treating articular cartilage injuries for patients in Vail, Summit County, Aspen, and Denver, CO.
When is Articular Cartilage Surgery of the Knee Needed?
When areas of articular cartilage are lost in a knee joint and there is exposed bone with no overlying coating cartilage, patients typically experience pain, swelling, and catching in the knee. These symptoms are worse after activities, particularly after impact activities such as running or skiing. As time progresses, areas of surrounding articular cartilage are overloaded and these areas start to wear away, leading to worsening symptoms. As a result, patients often find that they can no longer comfortably do the activities that they enjoy in life.
Initially, nonsurgical treatments such as icing, eating an anti-inflammatory diet rich with a lot of whole plant foods, modifying activities, wearing a knee brace, physical therapy, natural and prescription anti-inflammatory medications, and injections (steroid, hyaluronate, platelet rich plasma, or stem cell) may be tried. If these treatments fail to provide sufficient relief, then surgery may be considered, especially in young patients who have lost areas of articular cartilage due to a sudden traumatic injury and not from slow wear and tear as a result of aging.
What Are The Most Common Types of Articular Cartilage Surgery?
- Microfracture: Microfracture is a simple surgical technique that has been around for several decades. In this technique, a small puncture is made in an area of exposed bone in a damaged joint. A variety of cell types emanate from the bone forming “fibrocartilage,” which is a mixture of cartilage, bone, and scar tissue. This fibrocartilage can serve as a patch that “fills the pot hole.” This surgical procedure can be done arthroscopically. The recovery is such that you cannot put weight on the leg for 8 weeks and a motion machine (a CPM) is used each day for 8 weeks to gently move the knee. The results of Microfracture surgery are fair. In most studies, it is found that the fibrocartilage patch can wear away back down to bone in a few years and the same painful symptoms may return. As such, Dr. Cunningham only considers Microfracture surgery for cartilage defects that are hard to access, and thus are not amenable to other cartilage procedures.
- Autologous Chondrocyte Implantation (ACI): ACI is a technique that has been around for over 20 years, but it has been further refined and improved over time. In this technique, an arthroscope is placed into an injured knee and two Tic Tac sized pieces of cartilage with some underlying bone are taken from peripheral areas of the knee. These biopsy fragments are then sent to a company’s lab in the U.S. where the cartilage cells are isolated and then multiplied thousands of times in culture over about 1 month. The company was recently allowed by the FDA to then implant the cartilage cells onto an absorbable membrane. This membrane with the implanted cells is then returned to the surgeon. The patient is then brought back to surgery, the knee joint is opened through a 3 inch incision, the area of exposed bone is prepared and the membrane with the patient’s cartilage cells is imbedded into the cartilage defect and secured in place with a type of human glue. The cells will then continue to multiply, harden and fill the defect with actual articular cartilage as well as some fibrocartilage. This cartilage fill is more durable and long lasting than the fibrocartilage that Microfracture results in.
- Osteoarticular Transplantation (OATs): OATs is a procedure very similar to changing the position of a hole on a golf green. A patient is taken to surgery and a 3 inch incision is made over the knee. The area of worn cartilage is sized. A circular core containing the worn cartilage and about a half inch of the bone underlying it is removed. A circular core of normal cartilage and a half inch of underlying bone of the same size is then harvested from a donor’s knee, and this plug is transplanted into the area prepared in the patient’s knee. In so doing, the patient gets a nice layer of normal cartilage where there was once no cartilage. For small defects, cores of the patient’s own cartilage and bone taken from the periphery of the knee joint can be used to fill a more central cartilage defect in the knee. OATs is a reliable technique, but there is some data to suggest that the donor cartilage layer will wear at a faster rate than the patient’s own cartilage.
- Osteotomy: Osteotomy in and of itself is not an articular cartilage surgery. However, it is often done in conjunction with one of the above mentioned articular cartilage procedures. Osteotomy is employed when a knee is mal aligned, typically correcting someone who is bow legged (in varus) or knock kneed (in valgus). If one of the above mentioned articular cartilage procedures is done, but a patient’s poor alignment is not corrected, then the articular cartilage surgery will inevitable fail prematurely. Osteotomy is a bone cutting procedure done to realign a knee and unweight areas of cartilage overload and wear. The most common osteotomies done are opening wedge tibial osteotomy (to correct a varus knee) or an opening wedge femoral osteotomy (to correct a valgus knee). Please see Dr. Cunningham’s article on osteotomies for more information.
What Is the Recovery After Articular Cartilage Surgery?
The recovery varies slightly depending on which of the above procedures is undertaken, but in general, patients are on crutches with no weight bearing allowed for 6-8 weeks. Gentle range of motion exercises are started immediately after surgery. A continuous passive motion (CPM) machine is often prescribed. Gentle strengthening exercises are started at 8 weeks. Most patients are back to most activities 4 months after microfracture surgery, 6 months after an OATs procedure, and 8 months after ACI surgery.
Although restoring normal articular cartilage in a damaged joint has been called “the Holy Grail of Orthopedics,” there have been some exciting advancements in these surgical techniques in recent years. Dr. Cunningham is an articular cartilage surgeon at Vail Summit Orthopedics and Neurosurgery. He is an expert at diagnosing and treating articular cartilage injuries for patients in Vail, Summit County, Aspen, and Denver, CO.