Knee Meniscus Tear
Normal Anatomy: Knee Meniscus Tear
The bones of the knee are the femur (thigh bone), tibia (shin bone) and patella (kneecap). The femur and tibia meet to form a hinge with the patella in front of these two bones protecting the joint. The patella slides up and down in a groove in the femur (the femoral groove) as the knee is bent and straightened.
Ligaments hold the knee together and give it stability. The medial (inner) collateral ligament (MCL) and outer (lateral) collateral ligament (LCL) limit sideways motion of the knee. The posterior and anterior cruciate ligaments (PCL and ACL) limit forward motion of the knee bones, keeping them stable.
Two structures known as menisci sit between the femur and the tibia and act as cushions or shock absorbers for the knee. Menisci are one of two types of cartilage in the knee. The other type, articular cartilage, is a smooth and very slick material that covers the end of the femur, the femoral groove, the top of the tibia and the underside of the patella. This articular cartilage allows the bones to move smoothly.
Tendons connect muscles to the knee. The quadriceps muscles on the front of the thigh are connected to the top of the patella by the quadriceps tendon, which covers the patella and becomes the patellar tendon. The patellar tendon then attaches to the front of the tibia. The hamstring muscles in the back of the leg attach to the tibia at the back of the knee. The quadriceps muscles straighten the knee and the hamstring muscles bend the knee.
Pathology
The menisci are two C-shaped cartilage disks that sit between the thigh bone (femur) and the shin bone (tibia) and provide stability, support, and cushioning for the knee. Through wear-and-tear or a specific injury such as during sports, the menisci can tear. These tears can be horizontal, vertical, oblique, circumferential, or a combination of all of these tear patterns. If a meniscus tear creates a flap of meniscus, it can then flip into and out of the knee joint, causing pain, swelling, catching, and/or locking-type symptoms. Losing the cartilage lining on the lower end of the femur or the upper end of the tibia can predispose a person to a meniscus tear as the space between the two bones gets smaller. In younger patients, a knee ligament injury can occur at the same time as a meniscus tear. A meniscus tear can also occur in conjunction with a special type of tibia fracture. X-rays will show any fractures, dislocations, or any evidence of arthritis. An MRI may be necessary to better image the ligaments, tendons, cartilage surfaces, and menisci to determine the extent of any injury to these structures.
Treatment
Meniscus tears can be treated non-operatively or operatively. If the tear is small, does not extend all the way through the body of the meniscus, and the patient is not having any catching or locking-type symptoms, non-operative treatment is recommended as the first course of treatment. Non-operative treatment involves a cortisone injection and a course of physical therapy to strengthen the muscles around the knee.
If non-operative treatment does not provide relief, the tear is large, extends to the joint surface, or the patient is having pain, swelling, catching or locking-type symptoms, operative treatment is recommended. In most cases, the meniscus tear is trimmed back to a stable rim, leaving the healthy meniscus tissue to provide support, stability, and cushioning for the knee. The torn meniscus tissue that is not functioning and only causing the patient symptoms is trimmed out, leaving all of the healthy meniscus tissue to function properly. After the surgery, physical therapists work with the patient to start moving the knee, strengthening the muscles around the knee and leg, and getting the patient back to their desired activities.
In younger patients, or patients that have had a specific injury that caused the meniscus tear, the tear can sometimes be repaired with a separate incision and stitches. If the torn meniscus can be repaired, the patient will not be allowed to put any weight on the operative leg for a period of time after surgery while they work with physical therapists and then weight-bearing on the operative leg will slowly be advanced. Therapists will work with the patient to start moving the knee, strengthen the muscles around the knee and leg, and will ultimately get the patient back to their desired activities.