An Update on Diagnosing Meniscal Tears of the KneeIf you watch much sports on television, you know that a torn knee cartilage (meniscus) can put a player on the bench. Injuries to the meniscus occur most often in athletes when they injure other parts of the knee (e.g., knee ligament tears, fractures around the knee). But did you know that most meniscal tears actually occur in older adults as a result of aging? That makes the diagnosis and treatment of degenerative meniscal tears an item of interest for many older adults and the doctors who treat them.
In this review article, three orthopedic surgeons bring us up-to-date on patient evaluation of meniscal injuries. Their focus is on the anatomy, biomechanics, and function of the menisci (plural for meniscus).
Taking a quick look at the anatomy of the meniscus, we find that it is a C-shaped disk of fibrous cartilage between the tibia (lower leg bone) and the femur (thigh bone). There are two menisci: one on each side of the knee joint. The medial meniscus (along the inside of the knee closest to the other leg) is torn most often. The lateral meniscus (along the outside of the knee away from the other leg) is injured less often.
The menisci have several functions. They help spread the load from forces directed from the foot up through the knee and into the hip. They act as mini-shock absorbers while lubricating the joint and helping the joint surfaces slide and glide smoothly against each other. Without these fibrocartilage disks, the knee is less stable and more likely to give way underneath the person. An unstable knee is at increased risk for another injury.
Diagnosis is made by history, physical exam, and imaging such as X-rays and MRIs. The patient's history will reveal his or her activity level, lifestyle, previous injuries, goals for recovery, and any other health concerns or issues. During the physical exam, the surgeon looks for loss of joint motion, tenderness along the joint line, and any swelling that may be present.
The patient's report of traumatic injury or the onset of popping, catching, locking, or buckling of the knee is suggestive of a meniscal tear. The patient who reports loss of knee motion and says it feels like the motion is blocked may have a torn and displaced meniscus. Limping while walking is a common clinical presentation when the meniscus is torn because the patient cannot put full weight on that leg.
X-rays show any fractures or loose fragments in the joint. X-rays also help the physician see what kind of shape the joint is in, how much degeneration has occurred, and any signs that the joint is thinning. MRIs show the pattern of meniscal tears. This helps the surgeon plan treatment. The tear could be across the meniscus (vertical), the length of the meniscus (horizontal), or at a diagonal (oblique). The severity of the tear can also be assessed with MRIs (mild, moderate, severe). Any other features such as the shape of the tear (e.g., flap tear, parrot-beak tear, or complex configuration) can be seen as well.
It is now recognized that removing a torn or damaged meniscus isn't always the best idea. With all of their functions to disperse load, absorb shock, stabilize the joint, and give controlled joint motion, it's no wonder the knee degenerates faster without the menisci. Early, degenerative arthritis is common in those patients who have a meniscectomy (surgical removal of the meniscus) after an injury. Every effort is made now to save these important cartilaginous disks.
Understanding the anatomy, biomechanics, and function of the menisci is important when trying to repair rather than remove them. The surgeon must be knowledgeable about the direction of the collagen fiber bundles that make up the menisci. Understanding microanatomy, blood supply, and location of nerve fibers is necessary when trying to surgically restore this important part of the knee.
Likewise, understanding motion of the meniscus as it is guided by ligaments and joint capsule and where and how the meniscus attaches to the bone are key features needed by orthopedic surgeons repairing torn menisci and restoring normal anatomy and function as much as possible. All of these aspects of the meniscus are discussed in detail with color illustrations and MRI photos to aid the surgeon in making a correct diagnosis.
A discussion of treatment for meniscal tears is not included in this article. The authors say this is an update of a previous article they published in 2005 on the diagnosis and management of meniscal injuries. A second article will be published in The Journal of Musculoskeletal Medicine later with a similar type review of treatment approaches to this problem. Both conservative (nonoperative) and surgical treatment will be discussed at that time.
John P. Goldblatt, MD, et al. Managing Meniscal Injuries: The Diagnosis. In The Journal of Musculoskeletal Medicine. September 2009. Vol. 26. No. 9. Pp. 343-351.
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