The meniscus is a commonly injured structure in the knee. The injury can occur in any age group. In younger people, the meniscus is fairly tough and rubbery, and tears usually occur as a result of a forceful twisting injury. The meniscus grows weaker with age, and meniscal tears can occur in aging adults as the result of fairly minor injuries, even from the up-and-down motion of squatting.
This guide will help you understand
- where the meniscusis located in the knee
- how an injured meniscus causes problems
- what can be done for an injured meniscus
What is a meniscus, and what does it do?
There are two menisci between the shinbone (tibia) and thighbone (femur) in the knee joint. (Menisci is plural for meniscus.)
The C-shaped medial meniscus is on the inside part of the knee, closest to your other knee. (Medial means closer to the middle of the body.) The U-shaped lateral meniscus is on the outer half of the knee joint. (Lateral means further out from the center of the body.)
These two menisci act like shock absorbers in the knee. Forming a gasket between the shinbone and the thighbone, they help spread out the forces that are transmitted across the joint. Walking puts up to two times your body weight on the joint. Running puts about eight times your body weight on the knee. As the knee bends, the back part of the menisci takes most of the pressure.
Articular cartilage is a smooth, slippery material that covers the ends of the bones that make up the knee joint. The articular cartilage allows the surfaces to slide against one another without damage to either surface.
By spreading out the forces on the knee joint, the menisci protect the articular cartilage from getting too much pressure on one small area on the surface of the joint. Without the menisci, the forces on the knee joint are concentrated onto a small area, leading to damage and degeneration of the articular cartilage, a condition called osteoarthritis.
The menisci add stability to the knee joint. They convert the surface of the shinbone into a shallow socket, which is more stable than its otherwise flat surface. Without the menisci, the round femur would slide on top of the flat surface of the tibia.
How do meniscal problems develop?
Meniscal injuries can occur at any age, but the causes are somewhat different for each age group. In younger people / athletes, the meniscus is a fairly tough and rubbery structure. Tears in the meniscus in patients under 30 years old usually occur as a result of a fairly forceful twisting injury. In the younger age group, meniscal tears are more likely to be caused by a sport activity. The entire inner rim of the medial meniscus can be torn in what is called a bucket handle tear. These tears usually occur in an area of good blood supply in the meniscus. When treated early (within 3 weeks) these can generally be repaired.
Displaced Bucket Handle Tear (A), Repaired meniscal tear (C)
The meniscus can also have a flap tear from the inner rim. These tears usually involve a small percentage of the meniscus and do not have the ability to heal because they occur in an area that does not have blood supply. These are usually “trimmed out” or “shaved”. The earlier these tears are treated, the less meniscus that has to be trimmed.
The tissue that forms the menisci weakens with age, making the menisci prone to degeneration and tearing. These changes generally begin in the early 30’s. People of older ages often end up with a tear as result of a minor injury, such as from the up-and-down motion of squatting, stairs, or even a misstep walking. Most often, there isn't one specific injury to the knee that leads to the degenerative type of meniscal tear. These tears of the menisci are commonly seen as a part of the overall condition of osteoarthritis of the knee in aging adults. Degenerative tears cause the menisci to fray and become torn in many directions.
With more advanced degenerative changes in the knee the roughness and irregularity of articular cartilage cap on the bone can actually be the cause of the meniscus tear. Particularly in these cases, physical therapy and strengthening and not arthroscopic surgery will lead to the active person’s best knee.
What does a torn meniscus feel like?
The most common problem caused by a torn meniscus is pain. The pain may be felt along the edge of the knee joint closest to where the meniscus is located. Or the pain may be more vague and involve the whole knee.
The knee may swell, causing it to feel stiff and tight. This is usually because fluid accumulates inside the knee joint. This is sometimes called water on the knee. This is not unique to meniscal tears, since it can also occur when the knee becomes inflamed.
The knee joint can also lock up if the tear is large enough. Locking refers to the inability to completely straighten out the knee. This can happen when a fragment of the meniscus tears free and gets caught in the hinge mechanism of the knee, like a pencil stuck in the hinge of a door.
A torn meniscus can cause long-term problems. The constant rubbing of the torn meniscus on the articular cartilage may cause the joint surface to become worn, leading to chondromalacia (softening of the cartilage) which is a precursor to Osteoarthritis.
How do doctors identify this problem?
Diagnosis begins with a history and physical exam. Your doctor will try to determine where the pain is located, whether you've had any locking, and if you have any clicks or pops with knee movement. X-rays will not show the torn meniscus. X-rays are mainly useful to determine if other injuries are present.
Magnetic resonance imaging (MRI) is very good at showing the meniscus. The MRI machine uses magnetic waves rather than X-rays to show the soft tissues of the body. This machine creates pictures that look like slices of the area. Usually, this test is done to look for injuries, such as tears in the menisci or ligaments of the knee. This test does not require any needles or special dye and is painless.
If the history, physical examination and MRI indicate a torn meniscus, arthroscopy may be suggested to treat the problem. Arthroscopy is an operation that involves inserting a miniature fiber-optic TV camera into the knee joint, allowing the orthopedic surgeon to look at the structures inside the joint directly. The arthroscope lets the surgeon see the condition of the articular cartilage, the ligaments, and the menisci as well as feel theses structures with a probe.
Initial treatment for a torn meniscus focuses on decreasing pain and swelling in the knee. Rest and anti-inflammatory medications, such as aspirin, can help decrease these symptoms. You may need to use crutches until you can walk without a limp.
Some patients may receive physical therapy treatments for meniscal problems. Therapists treat swelling and pain with the use of ice, electrical stimulation, and rest periods with your leg supported in elevation. Exercises are used to help you regain normal movement of joints and muscles.
If the knee continues to be painful, keeps locking up, giving out or can't be straightened out, surgery may be recommended as soon as reasonably possible to remove the torn part that is getting caught in the knee joint. But even a less severely torn meniscus may not heal on its own. If symptoms continue after nonsurgical treatment, surgery will probably be suggested to either remove or repair the torn portion of the meniscus.
Surgeons use an arthroscope (mentioned earlier) during surgery for an injured meniscus. A small incision (about 5 mm) is made in the knee to allow the insertion of the camera into the joint. A second small incision is made to insert small instruments such as shavers, probes and biters to perform any necessary procedures.
The procedure to take out the damaged portion of the meniscus is called a partial meniscectomy. The instruments mentioned above are used to remove the torn portion of the meniscus, while the arthroscope is used to see what is happening.
Knee Arthroscopy Removal of Torn Meniscus
“Balancing” the meniscus (leaving smooth rounded edges) and trimming the meniscus tear back to good quality meniscal tissue is important in order to minimize the chance of having a re-tear of the trimmed meniscus.
Whenever possible, surgeons prefer to repair a torn meniscus, rather than remove even a small piece. Young people who have recently torn their meniscus are generally good candidates for repair. Older patients with degenerative tears are not.
To repair the torn meniscus, the surgeon inserts the arthroscope and views the torn meniscus. Some surgeons use sutures to sew the torn edges of the meniscus together. Others use special fasteners, called suture anchors, to anchor the torn edges together.
Nonsurgical rehabilitation for a meniscal injury typically lasts six to eight weeks. Therapists use methods such as electrical stimulation and ice to reduce pain and swelling. Exercises to improve knee range of motion and strength are added gradually. If your doctor prescribes a brace, your therapist will work with you to obtain and use the brace.
You can return to your sporting activities when your quadriceps and hamstring muscles are back to nearly their full strength and control, you are not having swelling that comes and goes, and you aren't having problems with the knee giving way.
What happens after meniscal surgery?
Meniscal surgery is done on an outpatient basis. Patients usually go home the same day as the surgery. The incisions are covered with surgical strips, and the knee will be wrapped in a bulky dressing with an elastic bandage over the top. It is common to see some blood appear on the outer part of the dressing the same day or sometimes the following day after surgery. DO NOT BE ALARMED IF THIS OCCURS. It is normal but if you are still worried, do not hesitate to call and we will reassure you.
The most effective thing you can do to return to normal walking without a limp is to keep the leg elevated and iced as much as possible for two to three days after the surgery.
SHOWERING: When you awaken the next day after surgery, feel free to remove your dressings and take a normal shower (if you are not scheduled for physical therapy). You may shower and allow the water to run over the operative knee and bandage strips. You should also let soap run gently over the operative incisions. Gently dab them dry when finished. Covering the puncture sites with small band-aids is only necessary if there is some drainage from the wounds.
CRUTCHES: Crutches are often used after meniscal surgery. They will usually only be needed for one to two days after surgery. Patients having a meniscal repair will wear a hinged-knee brace when walking that keeps the leg in full extension (leg straight) for 4-6 weeks. You are instructed to use the brace in the ‘locked’ position while walking. You may weight bear as tolerated (ie., place as much weight as they comfortably can) on the surgically treated leg.
Patients who have had a meniscal repair usually wear a knee brace for at least four weeks. The brace keeps the knee straight. It is removed several times during the day to do easy range-of-motion exercises for the knee.
Avoid doing too much, too quickly. Using cold packs on the knee is the most effective way with the least side effects to help control pain. The knee may be iced 20-30 minutes out of the hour or more if pain is significant. Keeping your leg elevated and supported is another good way to minimize swelling and pain.
After partial meniscectomy or meniscal repair, you will be instructed to place a comfortable amount of weight on your operated leg using a walking aid (i.e. crutches or cane). Patients will usually need physical therapy visits after meniscectomy. The length of physical therapy will depend both on the complexity of work done inside the knee as well as how strong and fit the patient was prior to the procedure. Rehabilitation is slower after a meniscal repair and in individuals who were not on a consistent fitness/strengthening program prior to surgery. Physical therapy will generally be three times a week in order to have the best recovery.