Knee: Meniscus tears.

Meniscus tears are common injuries of the knee. As I was driving home this Thanksgiving week, 2013, I heard about Mr Derrick Rose's meniscus tear. I am not into sports, not the professional sports anyhow. But I did look him up, and I understood the significance of this particular meniscus tear for the professional basketball scene of Chicago.

It was striking to hear the host on WBEZ admit that she had no idea what a meniscus is. And so I dug up some arthroscopy pictures from my patients and wrote this page.

First things first

The word meniscus comes from the Greek word for "crescent."

The meniscus of the knee is also known as semilunar cartilage, not to be confused with the articular cartilage. Each knee has 2 of these things, a medial meniscus and a lateral meniscus (one on each side of the knee).

Each meniscus sits at the edge of the knee joint, between the femur and the tibia.

A picture is worth a thousand words. Here is a look of a normal medial meniscus of a left knee with a camera placed inside the knee of a 25 year old patient. The meniscus starts out thick and bulky at the edge of the knee, and thins out towards the center.

What does a meniscus do?

The word "shock absorber" is sometimes used to describe the function of the meniscus, but the other weight bearing joints of the body do not have such "shock absorbers"

What is known for sure, and it has been known since the 1940's thanks to the work of Dr Fairbanks, is that a knee without a good meniscus becomes arthritic quickly.

Look at the picture above, and note how round the medial femoral condyle is, like a ball; note that the tibia is concave but shallow. The rubbery meniscus sits between the two and completes the joint. We think that without the meniscus, the weight bearing pressures inside the knee are concentrated on spots of articular cartilage. This then results in premature wear of the articular cartilage.

I have a meniscus tear. Do I need surgery?

Perhaps.

Arthroscopic surgery may help repair the torn meniscus, or may help remove irrepairable meniscus fragments. The process of removal of torn meniscus fragments is known as meniscectomy.

Whether either a meniscectomy or a repair of meniscus is necessary depends a lot on the type of meniscus tear. There are two kinds of meniscal tears

  1. Degenerative meniscal tears
  2. Traumatic tears in younger patients
Degenerative meniscus tears

The degenerative meniscus tears are more common. These tears occur from aging of the knee, from the millions of daily steps and tiny little injuries accumulated over the years. These degenerative meniscus tears are associated with knee arthritis. Whether they cause the arthritis, or whether they are caused by arthritis, is a true chicken-and-egg problem.

When I diagnose a patient with a degenerative meniscus tear, I give them 3 options

  1. Nonsurgical treatment with NSAIDs, activity modification, occasional cortisone injections, etc. It is best to think of a degenerative meniscus tear as part of the arthritic disease, not necessarily a problem in and of itself. Faced with a degenerative meniscus tear, it is best to treat the arthritic process as a whole, not just the meniscus "tear". In the setting of arthritis arthroscopic surgery may provide only short-term relief or may not help at all.
  2. Arthroscopic meniscectomy. In some situations, a degenerative meniscus tear can effectively act as a loose body inside the knee, and can be a problem in and of itself. Arthroscopic meniscectomy is a reasonable option if the torn meniscal fragments cause locking of the knee, frequent painful snaps, frequent swelling, etc. In these situations, removing such meniscus fragments will help immensely.
  3. Meniscus repair. Even a degenerated meniscus sometimes is amenable to repair, as opposed to meniscectomy. Degenerative meniscus tears typically are not repaired because the quality of meniscal tissue is poor. Nevertheless, a fully informed patient may still wish to try repairing (as opposed to removing) a degenerative meniscus.
Traumatic meniscus tears

These typically occur in younger patients due to forceful motion of the knee.

Due to the energy of the injury, the traumatically torn meniscus is widely displaced and produces severe symptoms. Surgical treatment is usually necessary.

Depending on the shape of the tear, these meniscal tears may be amenable to repair, or not. The determination to repair or remove the torn meniscus is made during the arthroscopy procedure, by looking at the torn meniscus with a camera.

How is a meniscus repaired?

Several different methods exist. Over the years, orthopedic device manufacturers have produced different kits which allow for all inside meniscal repair techniques. These kits work by using plastic darts which are used to anchor the sutures to the soft tissues around the knee.

However, as of 2013, the gold standard for meniscus repair remains something called inside out meniscus repair.

During the inside-out repair, a double barrel cannula is placed on the meniscus. A suture with two very long needles on each end is then passed through this double-barrel cannula. The long needles go all the way from the front and come out to the back of a the knee through an additional small incision. This ends up placing a suture loop through the meniscus. The suture loop is tied in the back of the knee, below the skin, thus ensuring secure attachment of the meniscus to the capsule.

The surgical technique is shown in the pictures below.

Meniscus repair case study

Same young patient whose normal medial meniscus you saw in the picture above above. The pictures below demonstrate the repair of his lateral meniscus.

His lateral meniscus was completely torn and displaced. This is known as a bucket-handle tear. The meniscus is torn from the back of the knee and is now way in front. Compare to the medial meniscus in the first picture.

In the following picture, a probe is placed through the medial portal and is used to nudge the meniscus back into place.

In the picture below, a double barrel cannula is then used to put a suture connected to two long needles through the meniscus. The needles are pushed all the way through and pulled out on the other side. The suture loop ends up on top of the menicus. The loop is then tied on the outside of the knee capsule. An incision in the back of the knee is necessary to safely catch and tie these sutures.

The process is repeated several times, on the upper and on the underside of the meniscus.

After this surgery, the patient uses crutches for 3 weeks. Weightbearing is not allowed. In addition, bending of the knee is limited to no more than 90 degrees for the first 3 weeks. Restrictions are gradually lifted 3 weeks after surgery.

Return to normal activity is gradual in order to avoid a retear.

At the end of the treatment, it is possible for the knee to be entirely pain-free or with only minimal pain. Full extension, is obtained most of the time. Limited flexion is commonly seen in these knees on at least a temporary basis.

The young man described above was seen in follow up more than 2 years after his meniscus repair and remains pain free.