Meniscus Injuries Part 1 - What Are You Dealing With
Knee pain caused by a meniscus injury is very common, in fact it may be one of the most common forms of knee injury. About 850,000 surgical procedures on the meniscus are performed each year (16). The good news is that all meniscus injuries DO NOT require surgery!
Just in case you were wondering, the word meniscus is derived from the Greek word that means “crescent” as in a crescent-shaped moon. Meniscal tears are one of the most common diagnosed knee injuries in North America. Some meniscus injuries do require surgery, others will heal with a combination of manual therapy and exercise.
WHAT CAUSES MENISCAL TEARS
Meniscus tears often occur in two ways:
1. The first is when playing sports such as football, basketball, soccer, or rugby. Quite often, the injury occurs during a torsional motion in which the player’s knee is flexed while the foot is planted on the ground. In such cases, the meniscus is torn due to the compressive forces that occur with rotation when the meniscus is compressed between the tibial and femoral condyles. Most of the time, a traumatic meniscal tear is a vertical or a longitudinal tear. Medial meniscus tears are also sometimes accompanied by an ACL (anterior cruciate ligament) and a MCL (medial cruciate ligament) tear (also called the “Terrible Triad or Horrible Triangle”). (11)
2. In the second case meniscus tears occur due to the slow degeneration that occurs during normal aging.
With age the meniscus becomes less pliable and is easily torn. This usually happens to individuals in their fourth or fifth decade of life. Degenerative meniscal tears are also more common in men than in women. (12).
Degenerative tearing of the meniscus is one of the most common causes of meniscus injury. In these cases the meniscus is often torn without the patient even knowing that it has occurred. With the degenerative process even common activities such as squatting could cause a tear in the meniscus (posterior horn of the medial meniscus).
RISK FACTORS FOR DEVELOPING OSTEOARTHRITIS
It is important to recognize that meniscus injuries can accelerate the chances of developing knee osteoarthritis. Although knee osteoarthritis is not life threatening, it can greatly affect the quality of your life.
Exercise Tip: We recommend that older patients avoid going to the point of maximum flexion when doing squats. Maximum flexion while doing squats (in older patients) has been correlated with an increased incidence of meniscal tears (12).
MENISCUS ANATOMY & BIOMECHANICS
The menisci in your knee are crescent-shaped, fibro-cartilaginous structures that provides stability, shock absorption, nutrition, and joint lubrication while acting to distribute your weight across your knee joint. Forty to sixty percent of the force in the lower extremity is transmitted through the menisci. Without functional menisci, the joints of the knees would soon degenerate. (5)
Each knee has two menisci - a lateral meniscus and a medial meniscus. Both menisci have a concave shape on the top and are flat on the bottom to create a wedge shape. Each meniscus is very thick on the outside, and very thin on the inside (almost paper thin on the inside). This wedge shape keeps your thigh bone [ femur] from slipping off your shinbone [ tibia].
The bones of your knees are covered with a layer of very smooth cartilage. This cartilage allows for gliding, reduced friction, and freedom of motion.
The menisci of your knees are located between these cartilaginous surfaces and act to provide stability and even weight distribution.
The medial meniscus is attached more securely than the lateral meniscus (which is more mobile). This secure level of attachment may be one of the reasons why there is a greater incidence of medial meniscus injury compared to the lateral meniscus. (15)
Bio-mechanically, we know that the meniscus of the knee follow the motions of the bones to which they are attached. Above the knee joint, the bones of the femur (femoral condyles) pull the menisci forward [anterior] with knee extension (knee straightening), and pull them backward [posterior] with knee flexion (foot towards your butt).
Below the knee joint, as the tibia rotates internally or externally, it pulls the meniscus with it. As the tibia rotates to the outside - the lateral meniscus is pulled forward while the medial meniscus moves back. If the tibia rotates to the inside the medial meniscus moves forward and the lateral meniscus moves back. (10)
The severity of a meniscus injury varies greatly depending on its location. Meniscus injuries, on the outer edges of the meniscus, can be very slow to heal due to poor circulation but can still heal.
Key Point: Only the peripheral 10% to 25% of the meniscus is vascularized. (2)
The center area of the meniscus is avascular, it is without circulatory input. Meniscus injuries that occur within the center of the meniscus do not have the ability to heal themselves since the center of the meniscus does not have a blood supply. Without a good blood supply, nutrients required for healing are not supplied to the area and waste by-products are not removed.
You could say that the meniscus have a design flaw (having such poor circulatory function), but then I would be taking a chance on being struck by lightning. Just joking!
DEGREE OF INJURY
Injuries to the menisci can range from minor, moderate, to more severe. Pain and swelling are the most common symptoms of a meniscus tear. Often a meniscal tear is described as a sharp stabbing pain as opposed to a dull ache. With more severe menisci injuries, a person may notice some degree of “locking of the joint” accompanied by considerable instability of the knee.
If “locking of the joint” occurs, it is imperative to immediately obtain medical attention from a sports physician, or some other medical practitioner who works with physical medicine. Your specialist should perform a physical examination on you to determine the severity of the injury.
Note: In a severe meniscus injury, loose pieces of cartilage (articular cartilage) may actually break off within the joint. These pieces can cause considerable damage to the knee joint, and lead to degenerative arthritis.
Symptoms are commonly aggravated by flexing and loading the knee. Complaints of clicking or a feeling of giving away are common. Any activity that requires kneeling, squatting, twisting or pivoting are poorly tolerated.
SYMPTOMS OF MENISCUS INJURY
The following gives you a basic idea of the symptoms associated with the severity levels of menisci injury. Please be aware that these are general guidelines, to make a definitive diagnosis a medical professional should be consulted.
Symptoms of a minor meniscus tear:
Only minimal pain - you are still able to walk.
Some degree of swelling with increased pain when squatting.
Most of these symptoms should diminish within 2-3 weeks of initial injury.
Symptoms of a moderate meniscus tear:
Pain directly at the site of the meniscus (along the lateral or medial joint line).
Sharp pain with any type of squatting or twisting motion of the knee.
If these symptoms are ignored and rehabilitation is not implemented it could take several months to a year before they go away.
Symptoms of a severe meniscus tear:
Immediate sharp pain, swelling, and stiffness in the knee.
The knee may lock into position. A locked knee can often be pathognomonic for a meniscus Injury. locking is often seen with a bucket handle type tear of the meniscus.
The patient is often unable to straighten the knee.
This is often a case for surgical intervention.
CONCLUSION PART 1
Meniscus injuries usually occur in one of two ways.
The first is where the meniscus is torn due to the compressive forces that occur with rotation when the meniscus is entrapped between two bones (tibial and femoral condyles).
In the second case meniscus tears often occur due to the slow degeneration that occurs with normal aging. With age, the meniscus becomes less pliable and is easily torn.
The severity of a meniscus injury varies greatly depending on its location.
Meniscus injuries, on the outer edges of the meniscus, can be very slow to heal due to poor circulation but can still heal.
Meniscus injuries that occur within the center of the meniscus do not have the ability to heal themselves, since the center of the meniscus does not have a blood supply.
Injuries to the menisci can range from minor, moderate, to more severe. Meniscus injury symptoms can often give us a some indication of the severity of the injury.
Note: References for Meniscus Injuries - Part 1 to 3" in Part 3.
DR. BRIAN ABELSON DC.
Dr. Abelson believes in running an Evidence Based Practice (EBP). EBP's strive to adhere to the best research evidence available, while combining their clinical expertise with the specific values of each patient.
Dr. Abelson is the developer of Motion Specific Release (MSR) Treatment Systems. His clinical practice in is located in Calgary, Alberta (Kinetic Health). He has recently authored his 10th publications which will be available later this year.
Dr. Abelson is the owner of Kinetic Health, a partner in BKAT Motion Specific Release, and a partner in Rowan Tree Books.