Meniscus

What is it?

• The meniscus is a C-shaped disc of fibroelastic cartilage that exists between the femur (thigh bone) and tibia (shin bone) in your knee.

• The meniscus serves as the “shock absorber” in the knee, functioning to disperse and transmit forces across the cartilage and increase congruency in the knee joint. It also acts as a secondary stabilizer of the knee.

• You have two menisci in each knee: the medial and lateral menisci

• The meniscus is anchored to bone at the anterior and posterior aspects (roots). It also has attachments to the surrounding capsule.

Evaluation

• Meniscal injuries are common. They are the most common reason for knee surgery.

• Meniscal injuries most typically present as pain localized to the joint line of the knee (inside/medial or outside/lateral).

• Occasionally there will be associated mechanical symptoms (clicking, catching, popping, or locking).

• Pain is often experienced at the extremes of motion (knee bent all of the way or out straight).

• Clinical evaluation typically includes:

  • X-rays

  • Thorough physical exam

  • MRI (if a tear is suspected)

Injury/Tear Types

• Meniscal tears can occur from a variety of mechanisms related to acute trauma (direct impact injury twisting, associated ligamentous injury, etc.), but also can occur as a result of degeneration (“degenerative tear”).

• Meniscal tears come in all shapes/orientations and sizes. The type and size of tear matters in terms of treatment. Small, stable tears do not necessarily need any surgery. Large, unstable tears, on the other hand, often do. Please see the pictorial representation of the tears for further explanation.

• Tear types:

  • Horizontal

  • Vertical/longitudinal

  • Flap tears

  • Root tears

  • Bucket handle tear

Treatment

• Non-operative vs operative

• Treatment depends on a multitude of factors:

  • Tear type and size

  • Tear location

  • Presence or absence of arthritis

  • Symptom correlation

• Surgical options:

  • Meniscectomy — trimming out of the torn portion of the meniscus, leaving behind as much good/non-torn meniscus as possible.

  • Meniscal repair — stitches placed inside the knee to stabilize the meniscus while it heals.

  • Meniscal root repair — stitches placed through the meniscus and threaded through a bone tunnel to repair the root back down to bone.

  • Meniscal transplant — salvage procedure to replace a nearly absent or extensively torn meniscus. There needs to be minimal to mild arthritis present for this to be considered.

• The meniscus is a poorly vascularized structure. It has a very limited healing capacity on its own. Peripheral tears (near the capsule/outside edge) have some healing capacity, but central and free edge tears have limited to no intrinsic healing ability.