What is a Discoid Lateral Meniscus?
A discoid lateral meniscus is a congenital variation of the meniscus in the knee joint. The meniscus is a C-shaped cartilage structure located between the femur (thigh bone) and the tibia (shin bone) in the knee joint. It serves several important functions, including cushioning the joint, distributing forces, and helping to stabilise the knee.
In most individuals, both the lateral (outer) and medial (inner) menisci are crescent-shaped. However, in some cases, the lateral meniscus may be abnormally shaped, taking on a more disc-like or circular appearance. This is what is referred to as a “discoid” lateral meniscus.
Here are some key characteristics and considerations related to a discoid lateral meniscus:
Anatomy
A discoid lateral meniscus is typically thicker and covers more of the tibial surface than a normal crescent-shaped meniscus. It can vary in shape and size but is often described as being “complete” (covering a larger portion of the tibia) or “incomplete” (covering a smaller portion).
Symptoms
Many people with a discoid lateral meniscus do not experience any symptoms, and the condition is discovered incidentally. However, some individuals may develop knee pain, swelling, popping or clicking sensations, and a feeling of instability in the knee. These symptoms may be due to the discoid meniscus interfering with normal knee joint function.
Diagnosis
Diagnosis typically involves a combination of a physical examination, imaging studies (such as MRI), and sometimes arthroscopy (a minimally invasive surgical procedure to directly visualise the inside of the knee joint).
Treatment
Treatment options depend on the severity of symptoms and the specific characteristics of the discoid meniscus. In cases where the discoid meniscus is asymptomatic and not causing any issues, no treatment may be necessary. However, if symptoms are present and affecting the individual’s quality of life, treatment options may include:
Physical Therapy: Exercises to strengthen the muscles around the knee joint and improve stability.
Medications: Pain-relief medications or anti-inflammatory drugs.
Arthroscopic Surgery: In more severe cases or if the discoid meniscus is causing mechanical issues in the knee, arthroscopic surgery may be recommended. During this procedure, the surgeon may trim or repair the abnormal meniscus to improve its function.
Case Example
A 15-year-old girl presents with a history of lateral sided knee discomfort and pain of her left knee.. The pain is intermittent and activity related. On further questioning, she said that this pain had been bothering her since the age of 4.
Clinical examination of the left knee showed no swelling in the joint, the ligaments were stable and the knee range of motions were full. There was mild posterolateral joint line tenderness. There was a “clunk” on the bending of her left knee.
MRI of the left knee showed a discoid lateral meniscus with a tear.
Left knee arthroscopy was performed.
A complete discoid lateral meniscus was found.
The medial meniscus is normal with a crescent C-shape.
The discoid lateral meniscus shows a tear at the posterolateral area.
If the entire discoid lateral meniscus is removed, this young girl will definitely develop early onset osteoarthritis of her knee lateral compartment.
The alternative was to remove the discoid lateral meniscus and prepare for a lateral meniscus allograft transplantation.
The best option, however, is to attempt to repair the torn portion of the discoid lateral meniscus and then saucerise it to a more normal looking crescent shaped lateral meniscus.
The torn portion of the discoid lateral meniscus was repaired with sutures.
The discoid lateral meniscus was saucerised to make it more crescent shaped.
This is how it looked at the end of this surgery.
