Different knee injuries can affect the meniscus. The meniscus is a small “c” shaped structure within the knee that represents itself as a piece of cartilage acting as a cushion in the knee joint.
The meniscus sits between the thigh bone (femur) and the tibia (shin bone) acting as a shock absorber—one of these is located on the outside of the knee (the lateral meniscus) and the other on the inside of the knee (the medial meniscus). The medial meniscus bears up to 50% of the load applied to the inside compartment of the knee while the lateral meniscus absorbs up to 80% of the load on the outside compartment of the knee.
The meniscus plays an important role in the knee because it aids in joint stability, helps protect ligaments against force and it provides lubrication. Years ago, it was a common practice to remove damaged meniscus following a knee injury. This frequently led to arthritis and other degenerative conditions including a “bow-legged” or “knock-kneed” deformity. Today, the meniscus is usually repaired if injured because orthopedic physicians agree that it plays a significant role in the overall health of the knee.
There are many variables a physician must look at when diagnosing a meniscus injury—including where the injury is located within the meniscus, the pattern of the tear, and how it was injured.
- Location: The front portion of the meniscus is referred to as the anterior horn, the back portion is the posterior horn, and the middle section is the body. A posterior horn tear is the most common meniscus injury. In addition, the meniscus is also broken down into the outer, middle, and inner thirds. Tears in the outer 1/3 area have the best chance of healing because blood supply in this area is the strongest and helps aid in the healing process.
- Tear Pattern: Meniscus tears also come in many shapes including horizontal, longitudinal and radial. A complex tear will involve more than one pattern.
- Complete vs. Incomplete Tear: In addition, a meniscus tear will be classified as complete or incomplete. A tear is complete if it goes all the way through the meniscus and a piece of tissue becomes separated from the rest of the meniscus. If the tear is still partly attached to the body of the meniscus, it is considered incomplete.
- Acute vs. Degenerative Meniscus Injuries: Meniscus injuries will be classified as acute or degenerative. If a person’s is bearing weight on his or her leg and the knee is bent, an acute meniscus injury will occur if the knee is forcefully twisted while in this state. Statistics show that about 61 of 100,000 people experience an acute tear of the meniscus. Degenerative tears of the meniscus are more common in older people. 60% of the population over the age of 65 probably has some sort of degenerative tear of the meniscus. These tears are most likely result from minor injuries involving regular or sporting activity. They eventually will weaken and become less elastic and may or may not present symptoms. (see Associated Injuries in Pediatric and Adolescent ACL Tears: Does a Delay in Treatment Increase Risk of Meniscal Tear?)
Symptoms of Meniscus Knee Injuries
Depending on the extent of the meniscus injury, pain will be mild to severe. Most patients will experience swelling and a throbbing or sharp, knee pain. In addition, a clicking or popping sound will be heard. If the injury is small, symptoms will usually go away without treatment.
Treatment for Meniscal Knee Injuries
Treatment for a meniscus knee injury will vary depending upon the extent and location of the meniscus tear. If the tear is small and the pain and other symptoms are minor, strengthening exercises and a small regime of physical therapy may be all that’s needed to recover. For a larger tear, knee surgery will most likely be required and recommended.
A large meniscus tear resulting from a longer or more traumatic injury that causes painful symptoms and mechanical problems with the function of the knee joint most often requires a meniscus tear repair surgery. Dr. Millett will perform meniscus repair arthroscopically.
In arthroscopic surgical repair for a meniscus tear, two tiny incisions will be made and a small camera inserted so the joint can be reviewed and the torn pieces of meniscus repaired and/or removed. The goal is to save as much of the original, normal meniscus cartilage as possible. During meniscus repair surgery, if the torn section of meniscus is removed, then it is known as a partial meniscectomy. If they can be repaired, then the torn edges are joined back together with suture or tacks.