Medial Meniscus Tear

The menisci are two C-shaped pads of cartilage in your knee — one on the inside (the medial meniscus) and one on the outside — that cushion the joint between your thigh bone and shin bone. They deepen the contact between the bones, spread the load evenly, and help the knee feel stable. A tear disrupts all of that. The inner meniscus tears about three times more often than the outer one, and tears are classified by their shape (longitudinal, radial, horizontal, flap) and by how they happened (sudden injury vs. gradual wear).

In younger patients, tears usually happen with a twisting or cutting injury — often alongside an ACL rupture. In middle-aged and older patients, tears are usually degenerative — the cartilage has gradually worn down with age, and the tear coexists with underlying osteoarthritis.

The meniscus has three blood-supply zones. Only the OUTER third — called the "red zone" — gets enough blood flow to heal reliably. The middle third heals inconsistently. The inner two-thirds get almost no blood flow and heal poorly on their own. Where the tear sits on this map matters enormously: a tear in the outer red zone in a young patient is worth repairing; a tear in the inner zone in an older patient is usually better trimmed out cleanly. Your age, your activity demands, and the tear pattern all factor in.

Sudden (acute) tears happen when the bent knee is loaded and twisted hard — pivoting in soccer, landing wrong from a jump. Gradual (degenerative) tears creep in over years as the cartilage loses its tough fiber structure with age.

• Medial or lateral joint-line pain, localized to one side of the knee
• Mechanical symptoms — catching, locking, or a sense of something moving inside the joint
• Pain with squatting, twisting, or rising from a chair
• Delayed swelling developing over 24—48 hours (in contrast to the immediate hemarthrosis of an ACL tear)
• A palpable click with deep flexion in some patients

Tenderness right along the joint line on the affected side, plus specific exam moves (the McMurray test and Thessaly test) that load the meniscus and reproduce pain. Standard X-rays rule out a fracture and check for arthritis. That last point matters: in patients who already have arthritis with a degenerative meniscus tear, arthroscopic surgery to clean up the tear is no better than structured physical therapy. Knowing that going in changes the conversation.

MRI defines tear pattern, length, location relative to the vascular zones, and associated ligament or cartilage injury. It is obtained when the diagnosis is uncertain, when operative planning is needed, or when symptoms do not improve with initial nonoperative care.

For degenerative tears and for most stable tears without true mechanical locking, a structured nonoperative trial is the standard first step.

Arthroscopic surgery is considered for acute tears with true locking, unstable tear patterns that are likely to propagate, or persistent mechanical symptoms after a structured nonoperative trial. Whenever tear pattern, tissue quality, and vascular zone allow, repair is preferred over removal — preserving the meniscus preserves the knee. Repair is most successful in younger patients, in the peripheral (red-zone) tear, and when performed alongside concurrent ACL reconstruction (JAAOS 2022;30:e1—e12).

Recovery depends on which procedure was performed. After a partial meniscectomy (removal of the unstable torn piece), weight-bearing is permitted as tolerated and most patients resume daily activities quickly; return to cutting and pivoting sport follows once strength and confidence return. After meniscus repair or root repair, protected weight-bearing and restricted flexion are required while the repair heals — this is not optional, and adherence directly affects the durability of the result. Return to sport after repair is later and more deliberate than after meniscectomy.

Preserving the meniscus, when feasible, lowers the lifetime risk of knee osteoarthritis compared with partial meniscectomy. Your OSI provider sets activity targets based on imaging, exam, and how the knee is responding — not on a fixed calendar.

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