It seems like lately everyone in my circle of friends either has, or knows someone who has, a knee injury. Of these people, a handful of them have cartilage tears. Often, I am asked what to do about it. Will I need surgery? What happens if I don’t get surgery? Will it get worse? Can I still run or play sports? Since I’ve been bombarded with these questions lately, and since I actually have a cartilage defect in my knee, I thought I’d give you a brief overview of the types of cartilage damage and what can be done for them medically.
First, let’s talk anatomy. There are two types of articular cartilage inside the knee. There is hyaline cartilage on the end of the femur (thigh bone) and on the back of the patella (knee cap), and along with a lubricant called synovial fluid, its purpose is to provide a smooth, frictionless surface during movement. Tears or holes in the hyaline cartilage are called osteochondral defects.
The cartilage on the top of the shin bone is the meniscus. This is fibrocartilage, and its purpose is shock absorption. Fibrocartilage has lots of layers of collagen fibers that make it able to bear large stresses in multiple directions. Tears here are commonly referred to as meniscus tears.
Both types of cartilage are mostly avascular and non-innervated, meaning they don’t have blood supply or nerves. On the upside, not having nerves somewhere means you can’t feel pain, on the downside, not having blood supply means a tear or defect in the cartilage can’t heal or regenerate with the body’s own devices. So, if there are no nerves in the cartilage, why do you feel pain if you have a cartilage injury? A defect in the cartilage means you are not going to have as much shock absorption or as smooth a surface for the bones to glide over when you have impact or move your knee. The force that is normally absorbed by the cartilage is now being felt by the bone, and bone has a lot of nerves, which means it hurts when it has too much pressure on it. Try it out---just push hard on one of your bones that’s close to the surface----ouch! Now imagine pushing on that bone hundreds or thousands of times with a force as great as your body weight, and you’ll understand how a knee with defective cartilage feels just walking around on a normal day. Multiply that force by four and you’ll feel the pain you’d get with running on that bum knee. Not a good idea, right?
So what do you do about a cartilage tear? There are several options. The number one preferred option is to not have to do anything surgically. If the tear is stable, meaning there isn’t a loose flap interfering with normal movement, or the defect is very small, you may be able to get away with just strengthening the muscles around the knee. The level of activity you are involved in will also determine the need for surgery. If you play sports or do activities where there will be quick changes of direction, pivoting/twisting on your knees, or repetitive kneeling, there will be a lot of stress on the cartilage and a small tear can turn into a big tear, so surgery may be the best choice.
If you do need surgery, you will definitely have physical therapy in your future to help restore your range of motion, strength, balance, power, and agility.
Here is a brief breakdown of the available surgeries:Debridement - The most simple surgery; performed arthroscopically so there is minimal scarring with 2 or 3 very small incisions, usually done on the meniscus to smooth out frayed edges or to remove loose flaps interfering with normal motion. Immediate full weight-bearing is allowed. Rehab is usually 2-3 times per week for 1-2 months. Relief can be temporary if you do high-impact or repetitive activity since no attempt to repair or replace the cartilage has been make.
Micro Fracture - The cartilage lesion must be small to moderate (1-5 cm²) and have well-defined edges; performed arthroscopically. Any loose or remaining cartilage in the defect is removed down to the bone, then a small awl is used to drill holes in the bone to promote bleeding around the defect. This stimulates cells from the bone marrow to fill in this newly created hole and will create scar tissue (a type of fibrocartilage). If the original cartilage defect was on the femur where there is normally hyaline cartilage, this newly grown cartilage is made of a different material and is not as strong, so it may wear out in a few years. There is a strict non-weight bearing period of 4-6 weeks after surgery and use of a machine that passively bends and straightens the knee. The muscles become extremely weak in this period of time, so rehab is extensive. Plan on 2-3 times per week for 6 months and return to athletic activity at 6 months to 1 year (running and non-contact activity around 6 months; competition in sports is usually closer to 1 year).
Osteochondral Allograft or Autograft Implantation - An autograft means they will harvest and use cartilage from your own body to fill in the defect; an allograft means they will harvest and use cartilage from a cadaver to fill in the defect. The cartilage lesion will be on the femur or patella and should be small to medium in size (0.5-3 cm²) for an autograft, but can be larger than 3cm for an allograft. First, the defect is cleared of loose edges and a small amount of bone under the cartilage is removed. The defect is very carefully measured to determine the exact width and depth that the graft cartilage will need to be. If they are using cartilage from your own body, they will take it from a healthy site in your knee that has a non-weight bearing surface. The graft will have a small layer of bone as well as cartilage and will be fit into the defect like a plug. The cons of using your own cartilage are that you may have pain or problems from the site where they removed the healthy cartilage. The pros are that it’s your own tissue, so the cartilage is an exact match to the type that used to be there before injury and your body is less likely to reject the new cartilage plug. The downside of the cadaver graft is that there’s a chance your body will reject the foreign tissue. The upside is that they can repair very large defects (3 cm up to the entire condyle of the femur --- trust me, that’s huge). Posteroperatively, you will have a strict non-weight bearing period of 6-8 weeks, and use of a continuous passive motion machine. Rehab will be extensive to restore strength, ROM, and balance. Plan on 2-3 times per week for 6 months and full return to activity in 6 months to 1 year.
Autologus Chondrocyte Implantation — This procedure can repair defects 2-10 cm² in size on the femur or patella and will require two surgeries. The first surgery is arthroscopic, and they will harvest a small piece of healthy cartilage from a non-weight bearing surface in the knee. They will also clean any loose edges around the cartilage defect. The small piece of healthy cartilage is sent to a lab where they will grow additional cartilage cells for a period of about 6 weeks. The second surgery will require one large incision over the site of the damaged cartilage and a second incision over the top of the tibia (shin bone) where they will harvest piece of periosteum (a tissue that covers your bone) roughly the same size as the cartilage defect. The periosteal patch will be sewn over the cartilage defect and the healthy cartilage cells grown in the lab will be injected into the defect and the patch is then sealed with fibrin glue. Often this procedure is done if patients have failed previous cartilage repair attempts. There is a strict non-weight bearing period of 6 weeks and use of a continuous passive motion machine after surgery. There will be extensive physical therapy needed to restore range of motion, strength, and balance and the full recovery is 12-18 months.
If you have any questions about Cartilage damage in the knee or surgical/non-surgical options, please email me at Erin@JointVenturesPT.com.
Treatment Options for Articular Cartilage Defects of the Knee, Detterline, Alvin, et.al. Orthopaedic Nursing, September/October 2005. Volume 24, Number 5.
Dutton, Mark. Orthopedic Examination, Evaluation, and Intervention. McGraw-Hill Medical Publishing Division, New York, 2004.