Knee Pain: Torn Medial Meniscus Sprain
The meniscus is a cartilage inside the knee joint. It has semilunar (sickle) shape and it's main purpose is to deepen the relatively flat surface of the upper end of the shin bone. The meniscus distributes the force around the knee joint. Actually the meniscus bears about 40% of the load transmitted through the knee joint. Also meniscus adds some stability to the knee joint.
What is the meniscus and what does it do?
The meniscus acts like a gasket between the femur and the tibia to spread out the weight being forces transferred from the thigh above to the leg below. The ability of the meniscus to spread out the force on the joint surfaces as one walks is important because it protects the articular cartilage from excessive wearing. Without the meniscus, the concentration of force into a small area on the articular cartilage can damage the surface, leading to degeneration, called osteoarthritis.
Also the meniscus helps with the stability of the knee joint. The meniscus converts the tibial surface into a shallow socket. A socket is more stable than a flat surface. Without the meniscus, the round femur would be able to slide on top of the flat tibial surface.
How the meniscus is torn
The meniscus can be torn in several ways. The entire inner rim of the medial (inner) meniscus can be torn in what is called a bucket handle tear. The meniscus can also have a flap torn from the inner rim, or the tear can be a degenerative tear where a portion of the meniscus is frayed and torn in multiple directions.
How does the meniscus cause problems in the knee?
Meniscus injuries can occur in any age group, but the causes are somewhat different for each age group. In younger people, the meniscus is a fairly tough and rubbery structure. Tears in the meniscus in patients under the age of thirty usually occur as a result of a fairly forceful twisting injury. In the younger age group, meniscal tears are more likely to be caused by a sport activity.
In older people, the meniscus grows weaker with age. The tissue that makes up the meniscus becomes degenerative and is much easier to tear. Meniscal tears in the older age group occur as a result of a fairly minor injury, even from the up and down motion of squatting. Degenerative tears of the meniscus are commonly seen as a part of the overall condition of osteoarthritis of the knee in the older population. In many cases, there is no one associated injury to the knee that leads to the meniscal tear.
What does a torn meniscus feel like?
The most common problem caused by a torn meniscus is pain. The pain may be felt along the joint line where the meniscus is located or may be more vague and involve the whole knee. If the torn portion of the meniscus is large enough, locking may occur. Locking simply refers to the inability to completely straighten out the knee. Locking occurs when the fragment of torn meniscus gets caught in the hinge mechanism of the knee and will not allow the leg to straighten completely. (Imagine sticking a pencil between the hinges in a door and trying to close it.)
There are long term effects of a torn meniscus as well. The constant rubbing of the torn meniscus on the articular cartilage may cause wear and tear on the surface, leading to degeneration of the joint. The knee may swell with use and become stiff and tight. This is usually because of fluid accumulating inside the knee joint - sometimes called water on the knee. This is not unique to meniscus tears, but occurs whenever the knee becomes inflamed.
How do we look into this problem?
Diagnosis begins with a history and physical. The examination will try to determine where the pain is located, whether or not locking has occurred, and if you have any clicks or pops as the knee is moved. X-rays will not show the torn meniscus. X-rays are mainly useful to determine if other conditions are present.
The MRI scan is very good at showing the meniscus. The MRI (Magnetic Resonance Imaging) machine uses magnetic waves rather than x-rays, to show the soft tissues of the body. With this machine, we are able to "slice" through the area we are interested in very clearly. Usually, this test is done to look for injuries, such as tears in the menisci or ligaments of the knee. This test does not require any needles or special dye, and is painless. If there is a uncertainty in the diagnosis following the history and physical examination, or if other injuries in addition to the meniscal tear are suspected, the MRI scan may be suggested.
Example of an injury
Imagine it's your first time alpine skiing. You come down the hill too fast, hit a bump, catch one ski in the snow and have your leg twisted outward. If you're unlucky, the ski patrol might wind up taking you the rest of the way down. Compression combined with rotation of the knee joint, whether it's during a skiing accident, a basketball pivot or something as ordinary as slipping on ice, is one of the most common causes of a meniscal tear, which is a tear in the fibrocartilage that makes up the two menisci in each of your knees.
Common symptoms of a meniscal injury
People who have this injury often feel a dull and constant pain in and around the knee when resting, but a sharp pain when walking or bending the affected leg. If the injury is severe, they may also experience debilitating pain that leaves them unable to walk. There may be some swelling as well, but this may take a few hours after injury before becoming apparent.
If you've got all those symptoms but don't remember experiencing any awkward leg twisting, you could still have a meniscal tear. In fact, chiropractors distinguish between traumatic tears, like those that happen in skiing accidents, and degenerative tears, which most commonly develop as people age.
To understand the difference between the two causes, think of the two menisci (the lateral, or outer meniscus, and the medial, or inner meniscus) working together to form a shock absorber. Traumatic events can overload this shock absorber, causing partial or complete rips. Degenerative changes, on the other hand, simply wear it out.
The latter occurs when the tissue that makes up the menisci dries out, becoming less elastic and less effective at absorbing forces and providing stability. This drying out is a natural aging process that researchers don't yet fully understand. It can make people susceptible to tears, even when they're just performing relatively routine, non-stressful activities such as dancing or squatting.
What age group does this effect?
While anyone at any age can suffer a traumatic meniscal tear, young adults appear to be more susceptible because of their more active lifestyles.
Degenerative tears, on the other hand, are most common in people in their late 50s or early 60s. Regardless of whether you're suffering from a degenerative or traumatic tear, however, studies suggest that conservative chiropractic care is often more effective than surgery for this type of condition.
What are the treatment options?
Surgery may be necessary for severe tears, however. It involves removing part of the meniscus and suturing or scaffolding a graft, possibly a collagen implant, in the knee to promote the growth of new tissue. This surgery is a last resort, and while it generally has good results, non-invasive chiropractic care should be your first choice as it involves a lesser risk of side effects.
If you suspect a meniscal tear, see Dr. Grisanti as soon as possible regardless of the amount of pain you feel. Tears to the menisci commonly occur with additional injury to surrounding structures, so your chiropractor should perform a thorough examination. Also, because there is poor blood supply to the inner edges of the menisci, tears in this region are infamous for healing poorly. The sooner you seek care, the better.
Reviewed on February 1, 2013