The meniscus is a very important structure within the knee. Tears of the meniscus are possible at age. For many years torn menisci have been removed. New techniques, and our improved understanding of the importance of the meniscus, have led to an increase in repair of the meniscus by surgeons trained in meniscal preservation.
There are two types of cartilage within the knee. The first is called hyaline cartilage, and is the white, tightly adherent cartilage that is on the ends of bones within a joint. The second type is called fibrocartilage, which is rubbery and pliable. The meniscus is a crescent shaped structure that lies between the femur and the tibia on each side of the knee, and is made of fibrocartilage.
There are two main types of injury to the meniscus. In younger patients it can be torn during a twisting injury of the knee, when it becomes forcefully entrapped between the femur (thighbone) and the tibia (shinbone). It can happen in association with other injuries to the knee, such as rupture of the anterior cruciate ligament.
As a person ages, the meniscus becomes subject to degenerative change, and becomes less pliable. A degenerate meniscus is prone to tearing, even with minimal trauma.
Acute tears are associated with a tearing or popping sensation at the time of injury, with swelling peaking some hours after the injury.
Meniscal tears are frequently associated with pain in a well-localized region along the joint line, either on the outside or inside part of the knee. They are also associated with knee swelling, catching, clicking, or locking of the knee. The pain is often a sharp, sudden stabbing pain, which comes on and then disappears rapidly, particularly with deep bending or twisting activity.
Usually, a careful history and examination are sufficient to make a diagnosis. X-rays can help to exclude a fracture or knee arthritis as the cause of the pain.
The diagnosis can by confirmed with an MRI scan, which can also identify the pattern of the tear, its exact location, and the presence of any other injurie
A radial tear is a sharp split on the edge of the meniscus. These tears are often trimmed to produce a smooth edge which doesn’t catch.
Parrot beak tears are similar to a radial tears, but more extensive. They can frequently catch and click. These tears are not repairable and are trimmed to smooth the edge.
Horizontal Cleavage tears occur in menisci which are undergoing degenerate change. They split the meniscus into two leaves. The tear usually extends to the periphery of the meniscus. They are treated with removal of one of the leaves.
Degenerate tears are complex, irregular tears in menisci which have undergone degenerative change. These are prone to re- tearing, and function poorly.
Simple trimming may help.
Initial treatment of meniscal tears is rest, ice, elevation, and compression (RICE). This is usually combined with simple analgesia such as a non- steroidal anti-inflammatory medication. Some tears, particularly those near the outer rim, can heal naturally. Patients with ongoing meniscal symptoms can be treated with surgery. The surgical options are dependent on the pattern of the tear.
The outer third of the meniscus a good blood supply (the “red zone”), but the inner two thirds has no blood supply. This means that injuries to the inner parts of the meniscus have a low capacity to heal. Preserving as much meniscal tissue as possible is highly desirable as absence of the meniscus can lead to arthritis in the adjacent hyaline cartilage with time. Younger patients have a greater capacity for healing, and also benefit the most from meniscal repair. Bucket handle tears of the meniscus which run parallel to the edge of the meniscus are the most readily repairable.
When the tear is irreparable, the margins of the tear can be resected to eliminate any unstable flaps causing pain. However, care is taken to resect the most minimal amount of tissue possible.
Loss of a large portion of the meniscus can lead to increased stress on the articular cartilage. This results in an increased risk of arthritis in the adjacent areas of the joint. This risk is much higher in younger patients, in lateral sided injuries, and in patients with an unstable knee. If the adjacent cartilage is already worn, then the likelihood of progressive arthritis is high. Thus the function and integrity of the meniscus needs to be preserved at all costs, and all suitable meniscal tears should be repaired.
However, most people seeking help with a symptomatic meniscal tear are affected by significant meniscal pain which limits their day-to-day function. This pain usually does not resolve spontaneously. In order to relieve these symptoms, some meniscus may need to be removed. A balance needs to be struck between the need to address the acute problem, and the potential for arthritis in the future.
Tears which run along the periphery of the meniscus in the red zone, such as bucket handle tears or separations of the meniscus from the capsule of the knee can heal spontaneously. This is less likely in a knee with other injuries such as a torn anterior cruciate ligament. Due to the importance of the meniscus, I advocate surgical repair to increase the likelihood of healing. Any stabilisation procedure such as ACL reconstruction is best performed at the same time, and has been show to increase the likelihood of healing.
This capacity to heal diminishes with age. After around 40 years of age the success of meniscus repair is reduced, but in an active individual attempted repair may be worthwhile.
The factors influencing whether the meniscus should be repaired include
The meniscus is attached to bone at each end of its C shape. Tears of the meniscus from the bone at these attachments, or complete radial tears can cause a rapid deterioration in knee function and severe pain. These are devastating injuries as they de-function the entire meniscus. Without repair, arthritis progresses rapidly, and most patients will require knee replacement within 5 years. However, only some of these are able to be repaired. The remaining meniscus must be in good condition so that it can be sutured back to bone using arthroscopic techniques. If the meniscus is not suitable, some pain relief may be obtained by removing the torn segment with arthroscopy.
An arthroscopy is an operation on the knee joint via “keyhole” surgery. A camera is inserted into the joint via a small 1cm incision (or “portal”), and the instruments via a second 1cm portal. Occasionally other arthroscopic portals may need to be used in addition to these.
Arthroscopy provides an unparalleled view of the knee joint, which could not be obtained without a large, invasive incision. The small incisions minimise post operative pain, allowing rapid return to function. It is usually a day-surgery operation.
Knee arthroscopy is performed under a general anaesthetic. A torniquet is inflated over the upper thigh to prevent any blood entering the knee joint space, which would hinder vision. A thin, long camera is inserted into the knee, and the image appears on a screen in the operating theatre. Instruments such as probes, shavers, scissors, and special sutures can be inserted to treat various problems within the knee.
The most arthroscopic common operation is to treat a torn meniscus. If the tear is not in a configuration amenable to repair, the torn edges must be stabilised so that they do not catch and pull, causing pain. This is done by trimming the edges of the tear to proved a smooth, round contour.
At the end of the operation, local anaesthetic is injected around the incisions, and they are each closed with a stitch or sticky strips.
The procedure time depends on the condition which needs treating. In general, most arthroscopies take around 30 minutes.
Most procedures are day-surgery. You will arrive on the day of the operation, and can return home the same day. Please ensure that you have arranged your transport home as you are not permitted to drive for 24 hours after the surgery.
Arthroscopy is not useful in treating arthritis.
Most patients walk out of the hospital on the day of surgery, usually with crutches or a stick. The bulky dressing is then removed, leaving the sticky waterproof dressings intact. You may get these dressings wet in the shower. If the dressings come loose, please replace them.
The knee is allowed to bend as tolerated. Most patients can perform their usual activities after a few days. Office workers return to work after 3–5 days. Heavy manual workers may require 1–2 weeks to be able to resume work. Driving is usually possible within a week, when the knee is relatively pain free and bending easily.
There may be some knee swelling for up to 6 weeks, as well as some mild discomfort around the incisions.
This will depend of whether the meniscus is repaired or trimmed. Meniscal repairs must be protected for 3 months to minimise motion and stress while they heal. I generally don’t use a brace, but limit bending to 90o for 6 weeks, and don’t allow weight bearing. After 6 weeks, weight bearing is permitted, as is full bending of the knee, but loaded squatting past 90o is not allowed for another 6 weeks. Office workers will generally be able to work a week following surgery, but manual workers may be unable to work for up to 3 months. Driving is allowed when the limb which is operating a pedal is pain free and able to weight bear.
Meniscal trimming is associated with a much faster return to function. Immediate weight bearing is allowed, with no restriction on bending the knee. Most office workers return to work within a week, and manual workers in 1–2 weeks. The limb is usually fully recovered within 4 weeks.
There are general risks associated with knee arthroscopy, as well as specific risks for meniscal trimming and repair.
These include adverse reaction to medications, pain, bleeding, infection, stiffness, blood clots in the calf (deep venous thrombosis or DVT), blood clots traveling from the calf to the lungs (pulmonary embolus).