Lateral Meniscus Tear

The lateral meniscus is the O-shaped fibrocartilage on the outer side of the knee. It covers a larger portion of the tibial plateau than the medial meniscus and is more mobile, which makes it somewhat less prone to degenerative tears but more prone to certain acute tear patterns. Lateral meniscus tears commonly occur in combination with ACL tears.

A discoid lateral meniscus — a congenital variant where the meniscus is abnormally wide and disc-shaped — is more prone to tearing and can cause the characteristic "clunking knee" in children and young adults.

Pain along the outer joint line of your knee is the hallmark symptom. Squatting, twisting, or deep bending often sharpens the pain. You may notice swelling that develops gradually over a day or two after the injury, and the knee may feel like it catches or locks during movement.

Many lateral meniscus tears occur alongside an ACL tear, so the initial swelling from the ACL injury can mask the meniscus symptoms. Once the knee begins to settle, persistent outer-side pain, a sensation of something clicking or shifting inside the joint, and difficulty fully bending or straightening the knee point toward the torn meniscus.

Lateral joint-line tenderness, pain on squatting and deep knee flexion, and a positive McMurray test at the lateral compartment suggest lateral meniscus involvement. MRI confirms the diagnosis, identifies the tear type, and evaluates the ACL and lateral compartment cartilage.

Same indications as medial meniscus: mechanical symptoms, persistent pain, locked knee, or a repairable tear in a young patient. Combined ACL-lateral meniscus tears are generally repaired at the time of ACL reconstruction.

External patient-education references and related OSI pages for additional background:

• Britannica — Cartilage
• Britannica — Knee (anatomy)
• AAOS OrthoInfo — patient education library
• OSI glossary — orthopedic terminology in plain language