Knee pain, representing a broad spectrum of injury, is one of the most common complaints heard in a sports clinic.  ‘Round these parts, we often wonder: “did I tear my cartridge?”   I feel entitled to say this, as having been raised here in cosmopolitan central KY, I am a regular perpetrator of our “unique” bluegrass diction and grammar.  Regardless, it is actually called cartilage, the cushion in our knees.  And, there are two types.  Articular cartilage is the white squishy stuff that covers the ends of our bones.  Meniscus is actually comprised of fibrocartilage.  When someone states that they “tore their cartilage”, they are most commonly referring to meniscus.  Below, we’ll outline the structure, function, and briefly outline injuries and treatment for the meniscus.

Derived from the Greek word for “crescent”, the Menisci are “C” shaped discs which reside between the end of the thigh (femur) and the top of the shin (tibia).   There are two, one on the inside (medial) and one on the outside (lateral).  They have a flat bottom to rest on the relatively level tibia and a concave surface to accept the rounded end of the femur.  They serve a role to disperse pressure and reduce friction.  Think about it in terms of PSI, pounds per square inch.  With a round surface contacting a flat one, there is a concentration of force.  Add the menisci, and now there is a broader surface upon which to share the load.  Both clinical studies and biomechanical research have proven the critical role of the menisci in distributing force and preventing arthritis.

Unfortunately, injuries to the meniscus are extremely common.  In fact, arthroscopy (“scope”) for a meniscus tear is the single most common surgery performed by orthopedists across the country.  Tears generally occur in two varieties: traumatic and degenerative.  Traumatic tears are often the result of an acute twisting or squatting motion that exceeds to ability of the meniscus to withstand the shear forces.  On the other hand, as we age our meniscus becomes more brittle and may develop fissures from less substantial trauma that can progress into degenerative tears.  Once a tear develops it may begin to move abnormally or become caught within the joint.

The most common symptoms of a meniscus tear are:
Pain and tenderness along the joint line (where the femur and tibia meet)
Swelling
Popping or clicking coming from the joint line (not the kneecap, which is very common)
The sensation that something is “locking up” or limiting knee motion

Diagnosis is generally made by a careful history and physical exam.  X-rays are used to rule out any fractures or bone abnormality as well as evaluate any degree of arthritic change.  It is a critical point to remember that degenerative meniscus tears are part of the arthritic process and any treatment isolated to the meniscus in the setting of advanced “wear and tear” may fail to produce meaningful results.  MRI is often used to confirm the diagnosis as this allows visualization of cartilage and tendons not seen on x-rays.  Studies find MRI roughly 90% accurate in this diagnosis.

To complicate matters, nature has not been generous with the healing potential of the meniscus.  Only the peripheral third of the meniscus receives nutrition from small penetrating blood vessels.  Therefore, the inner two thirds are essentially without healing potential in the form of vital platelets, growth factors, and oxygen.  Treatment for meniscus tears should be directed on an individual basis after thoughtful discussion with your surgeon.  Tear pattern, severity of symptoms, activity level, arthritic changes, and response to simple measures should be considered.  Rest, anti-inflammatories, activity modification, injections, and numerous other modalities are often employed in attempts at non-surgical care.

When surgery is necessary it is usually involves arthroscopy and trimming of the torn portion (partial menisectomy).   In appropriately selected patients, results are good.  Recently, and coinciding with our growing understanding of function, orthopedists have become much more aggressive concerning attempts at meniscus repair.  However, despite surgeon desire to preserve meniscal tissue, patients and tear patterns are often not amenable.  In addition, meniscus repair will place significant restrictions on post-operative recovery and rehabilitation.  Finally, meniscal transplantation, from both cadaveric and synthetic sources, is available for symptomatic patients who have lost the majority of a meniscus to injury.