What is the meniscus ?
The meniscus is a small C shaped structure which sits between the femur bone and tibia bone. You have two in each knee: One on the inside and one on the outside. There was a time when it was thought to be unneccary – like an appendix – and removed completely whenever it caused a problem. This ended around 1980 when several landmark research studies were published explaining the importance of the meniscus and its role in knee function. Meniscus tears are extremely common: This may be the most common reason to visit my office!
Makeup of the meniscus
The meniscus is made up of thousands of tiny fibers called collagen. These are specially arranged circumferentially and attached to the top of the tibia bone in the front and back of the knee. The material in the meniscus is similar to ligaments but customized for the specific purpose of helping to tranfer pressure between the femur (thigh bone) and tibia (leg bone). This collagen is similar to the collagen found in cartilage that caps the bones of all joints. It is very strong and good at resisting a pulling force on it.
Function of the meniscus
This may get technical. The job of the meniscus is to distribute force across the top of the tibia bone when you walk, stand, or run. When the rounded femur bone comes into contact with the mostly flat tibia bone, the meniscus is tensioned around the periphery. This generates hoop stresses in the meniscus that are resisted by the collagen fibers oriented just right to these these forces. By spreading out the pressure across the joint, the stress felt by the cartilage is lower and less likely to cause damage to the joint. When the meniscus has been removed, the contact stress increases and can cause premature failure, or breakdown, or the joint surface. This leads to osteoarthritis.
How will I know if I have a meniscus injury ?
Because the meniscus can take up a lot of physical pressure, is not as strong as the joint surface, and is quite mobile, it is highly suseptible to injury. This can happen a few ways. The most common mechanism to tear is a sports injury when the knee is forced to rotate and the meniscus gets caught and torn. I see this frequently in soccer players, basketball players and the classic weekend warrior. It can also tear as a result of degenerative arhtritis in which it is weakened over time and can fail. There is often a popping sensation in the knee. The knee may begin to click and pop. The joint usually fills up with some fluid later that day or the next.
Meniscus tears cause intermittent activity related pain, catching and locking. It can feel like an ice pick in your knee. Sometimes the knee can become stuck and not able to bend or straighten at all. If you have this sensation, you will never forget it
Arthroscopic view of a meniscus tear
After arthroscopic removal of torn meniscal tissue
Diagnosis of a meniscal tear
Diagnosis of a meniscus tear is done in conjunction with several key factors. First your story, or history, makes sense for a twisting injury to the knee. Second, the pain of at ear is farily constant and does not improve over time. Next, the physican exam shows tenderness along the joint line and a positive McMurray’s Test, pain with deep flexion and often pain with full extension.
An MRI scan is often obtained to confirm a meniscus tear when suspected. This painless test gill show any obvious tears
MRI Image of a meniscus tear
This is a cross section of a knee on MRI. Its called a ‘sagittal’ cross section, as if viewed from the side of the knee. The meniscus should be a solid black triangle. See how there is a white line inside the trangle? This is the line of the tear.
Will a meniscus tear heal on its own ?
When should I see a doctor ?
You should be seen by an orthopedic surgeon if you can’t walk, if your knee is stuck and won’t bend, have pain that prevents you from routine activities, can’t sleep, or when the pain just won’t go away. If tolerable, I will often give patients 6 weeks to see if they get better. Or if you are just worried about your knee, please come see me or your orthopedic surgeon.
Treatment of a meniscus tear
First line treatment of tears is to calm down the knee. Rest, keep your foot up and elevated, try to minimize walking if possible, use an ice pack, and and ACE wrap. Sometimes taking 600mg if ibuprofen is a good idea. I often use a physical therapist to help guide you through the entire recovery process after a meniscal injury.
When is surgery needed for a meniscus tear ?
There are times when surgery is the right thing. This is not the same time for everyone. If you are not getting better with nonoperative treatments and continue to be limited in what you do, it’s time to think about surgery. This is definitely something to talk with your surgeon about to see where you are in the healing process after a meniscal tear. In making the right decision we must consider the potential benefit of having it treated against the risk of having the procedure. Fortunately, arthroscopic knee surgery is not a high risk procedure in general and when nothing else is working, its worth having the conversation with me or your surgeon.
What are the surgical treatments for a meniscus tear ?
Arthroscopic surgery for a meniscus tear is extremely common. This is done as an outpatient procedure – most people are at the surgery center for about 2 to 3 hours. The surgery itself takes anywhere from 10 to 20 minutes. It is done by making three small incisions about 4mm long around the knee. A small camera on a fiber optic rod is placed in the knee and tiny instruments are used to either repair, meaning sew back together, or trim away the torn unstable tissue. Look over the pictures above as you can see an example of the torn meniscus and what it looks like after trimming it back to normal intact tissue. You will be home soon and on the road to recovery the same day.
What is the rehabilitation for a meniscus tear ?
Rehabilitation for a meniscus tear , or any orthopedic condition, is key. I’ve written more about this:
The goal is to get you back to 100% as quickly as possible. I like to involve a physical therapist for many patients to help guide the process. Step 1 is get the swelling and inflammation down. Step 2 is work on flexibility. Step 3 is restore normal strength. I usually suggest a few days to a week of work for most people. If you are very phyiscally active at work, it may take a few more weeks before you are back to normal. I have performed 1000’s of these procedures, and yet every patient is unique.
Please ask me specifics about meniscus tears if you have questions. Remember if you are not my patient you cannot consider this specific medical advice.