The meniscus is a pliable substance made up of soft tissue that sits between two bones of the knee joint, the femur (thigh bone) and tibia (shin bone). There are two, crescent-shaped menisci in the knee, one on the inside of the knee (medial meniscus) and one on the outside of the knee (lateral meniscus). Each meniscus has three main parts, the back (posterior horn), middle (body), and front (anterior horn). Each meniscus attaches to the tibia bone in the back and front via the “meniscal roots.” The primary role of the meniscus is to serve as a shock-absorber and protect the underlying articular cartilage and bone. The meniscus has additional roles, including joint stability and joint lubrication.
In some individuals, the meniscus is not crescent-shaped, but instead is shaped more like a pancake. This condition is called a discoid meniscus. A discoid meniscus usually occurs in the outside compartment of the knee (lateral compartment). The incidence of this condition is approximately 1% in North America. Most individuals who have a discoid meniscus do not have any symptoms and have a stable knee. However, a discoid meniscus is prone to tearing. If an individual develops a tear of a discoid meniscus, he/she will likely develop symptoms.
- Pain and swelling on the outside of the knee
- Audible click in the knee
- A sense of instability in knee with side to side motion
Diagnosis And Treatment
Dr. Welch considers each patient’s symptoms, as well as a detailed physical examination, x-rays, and usually and MRI of the knee to make the diagnosis of a discoid meniscus. Some patients with a discoid meniscus tear can be treated with a combination of activity modification and a focused physical therapy program. Physical therapy focuses on maintaining knee range of motion and strengthening certain muscle-tendon unit that provide stability to the knee, such as the quadriceps and hamstrings. Other patients with persistent symptoms require surgery.