Illustration looking down on the top of the tibia bone, with the femur cut away, to show the menisci seated on the tibial plateau.
What is the difference between lateral meniscus and medial meniscus?
The lateral meniscus differs considerably from the medial meniscus. It is O-shaped, rather than C-shaped, and is much more mobile than the medial meniscus and there is much less attachment around the outer rim to the capsular walls.
In addition, the tendon of the popliteus muscle passes between the outer rim at the back of the meniscus and the capsule.
This illustration is from the back of the knee, looking at how the tendon of the popliteus muscle on the lateral side pierces the capsule and passes alongside the lateral meniscus on its way to insert on the femur. There is no equivalent on the medial side.
This complex area is called the 'posterolateral corner'. Injuries here may be a challenge to the surgeon.
What does the lateral meniscus do?
Both lateral and medial menisci act as shock absorbers and stabilisers of the knee joint.
Both are packed with fibres which are arranged in a structured network which makes the structures strong and help them avoid stress tears. The wedge-shape, and the presence of ligamentous attachments to the underlying tibia bone, help to stabilise the joint.
"....The lateral meniscus is a unique structure of the knee joint, and its anatomy, function, pathological process, and treatment are distinct from those of the medial meniscus...."
Can you walk with a lateral meniscus tear?
One can still walk with a lateral meniscus tear, although tears involving the posterolateral corner may be associated with feelings of instability.
Can a lateral meniscus tear heal by itself?
Small lateral meniscus tears may heal, but tears of the posterolateral corner are much less likely to heal on their own.
The person may develop some bowing of the knee compared to the other side, and experience uncomfortable instability.
How serious is a lateral meniscus tear?
A lateral meniscus tear is potentially a lot more serious than a medial meniscus tear because of its particular vulnerabilities.
The high mobility, the weaker outer rim and the poorer attachment to the capsule render it prone to instability once it is injured.
The clinician must be sure to exclude other conditions that may mimic a lateral meniscus tear.
"Common extra-articular pathologies that can mimic lateral meniscal tears include iliotibial band syndrome, proximal tibiofibular joint instability, snapping biceps femoris or popliteus tendons, and peroneal nerve compression syndrome or neuritis."
Other relevant links
Medial meniscus, Popliteus tendon, Capsule, Posterolateral corner, Posterolateral rotatory instability
Forum discussions
- I took the plunge, Lateral Meniscus Transplant + OATs - A personal story of a patient who's joint surfaces were under stress because of serious damage to the lateral meniscus.
- Extension deficit. - A young mother is struggling after partial lateral meniscectomy