Torn Cartilage: One Of Many Variations In Knee Injuries

One of the common knee surgeries athletes and physically active individuals have is related to the semilunar cartilage (miniscus). A tear in the meniscus (semilunar cartilage) is often referred to as a "torn cartilage". This can be confusing as there is more than one type of cartilage inside the knee.

The illustration depicts the two menisci that are in each knee. The menisci are described by indicating their position in the knee: medial and lateral. The medial is on the side nearer the midline of the body, while the lateral is along the outer side of the knee (away from the midline of the body). They rest on the tibia (shin bone) and are attached at their margins. The medial meniscus is torn more frequently than the lateral because of its attachment, size and location.

The meniscal attachments to the ligaments and capsule of the knee are important in its complex motion. Knee motion is more than a simple bending and straightening. There is some rotation and gliding motion between the femur and the tibia during a complete arc of motion of the knee.

The menisci have several functions. They increase joint congruity, enhance joint stability, serve as simple shock absorbers, and help spread the synovial fluid (joint lubricant).

The knee menisci are a special type of moon- shaped fibrocartilage. They have a nerve and blood supply along their outer edge but the inner two-thirds receives its nutrition from the fluid inside the joint. A tear in this portion of the meniscus without a blood supply does not heal by itself and often enlarges with time. A tear in the peripheral margin of the meniscus has the potential to heal if repaired. An additional small incision, or incisions, are usually required to satisfactorily repair (suture) the torn meniscus. The decision to repair a tear is frequently made at the time of surgery based on the location and extent of the tear.

If a meniscus (semilunar cartilage) is torn and displaces, it can interfere with the knee motion. The incapacity may be sudden and complete. The term the knee is "locked" means part of the motion is blocked. Most frequently this is associated with an inability to straighten the knee. These sudden and dramatic tears may occur with arising from a squatting or kneeling position, a sudden twisting motion of the knee, or a quick change of direction during athletic participation. They occur frequently and may occur when least expected. The meniscus injuries most commonly seen are usually not the dramatic ones that cause complete incapacity. They are more subtle and chronic in nature. Different types of small and/or complete tears may exist in the semilunar cartilage giving varying symptoms. These symptoms may include pain along the joint line, intermittent locking, a giving-way sensation, swelling, clicking, night pain, pain on squatting or pivoting, and the inability to duck walk. It is important to state that each of these, or all of these, symptoms can be produced by problems in the knee other than a "torn cartilage".

Diagnosing a tear in the meniscus may be straightforward in some cases and it may be difficult in others. Besides doing a detailed history and examination, the physician has special examinations available that may assist in clarifying the diagnosis. One is called an arthrogram, which is an x-ray study in which dye (and sometimes air) is placed inside the knee to outline the meniscus. The menisci are not delineated on a regular X-ray. The dye will flow into the tears and demonstrate their presence. The arthrogram is not 100 percent accurate and must be coupled with the clinical picture.

A new revolutionary imaging technique of the knee which may be ordered is Magnetic Resonance Imaging (MRI). An MRI provides a means of visualizing the menisci in a painless, non-invasive manner without exposure to radiation. The MRI utilizes powerful magnets to generate a magnetic field which induces hydrogen atoms in the tissue to align themselves in a predictable manner. As the magnetic field fluctuates, the hydrogen atoms "flip" back and forth between their normal random alignment and their magnetically induced alignment. A sophisticated computer gathers and assimilates data to produce high resolution pictures of the structures within the knee. Although MRI is quite versatile it is contraindicated in patients with intracranial vascular clips, pacemakers, and some prosthetic cardiac valves. Patients with claustrophobia may have difficulty tolerating the close confines of the MRI scanner. Even though MRI represents state of the art technology, it too lacks 100 percent accuracy and must be correlated with the clinical impression.

The arthroscope is a fiber optic system that can be used to look inside the knee. It requires some form of anesthesia and many patients choose to be put to sleep (general anesthesia). It is a surgical procedure and is performed on an outpatient basis. Usually arthroscopy is not necessary to diagnose a routine meniscus problem, but can be of assistance in a confusing case. Advances in arthroscopy allow the meniscal surgery to be performed at the time of arthroscopy. This results in smaller incisions, less time in the hospital, quicker return to sports and work, and less discomfort. Not all tears of the meniscus produce symptoms and not all tears require surgery. A meniscectomy is the name of the surgical procedure for removing the torn cartilage, or a portion of it. While surgical intervention is elective, the joint surface (articular cartilage) may sustain microscopic damage each time it rides over the incongruity of a torn meniscus. The damage is cumulative and early surgical treatment is sometimes desirable. Removal of the injured portion of a meniscus does not completely eliminate the accelerated wear, but has the potential to slow the progression. After a portion of the meniscus is removed, an attempt is often made by the body to form another one, but this is usually quite limited. Most active individuals do well after their meniscal surgery, but there are many reasons for the differences between individual recoveries. Two tears are seldom alike. Associated injuries to other structures in the knee, the duration the tear is present, and the presence of arthritis in the knee are among just a few of the factors which alter the recovery time. The resumption of athletic participation varies from one week to three months following removal of a portion of the meniscus. This is assuming there are no complications.

In conclusion:

1. Not all tears in the meniscus require surgery.
2. Not all knee problems are related to a torn meniscus.
3. A tear may be present suddenly and be incapacitating, or it may become more noticeable over a period of time.
4. The incidence of tearing a meniscus while participating in athletics is small, but it does occur. Tears occur in the work place and with the activities of daily living.
5. Playing sports may aggravate an old tear.
6. A symptomatic tear in the semilunar cartilage of the knee treated surgically usually results in a return to full activity in most instances.
7. Arthroscopic surgery offers a quicker return to sports and work than traditional open methods.