How common is it to tear your meniscus when part of it has already been removed?

Depends: The re-tear rate is highly variable. The age and activity level of the patient, quality of remaining meniscal tissue, type of tear and length of time since surgery all affect the rate. Typically, once the torn portion of the tissue is removed, if a stable and smooth edge of tissue remains then re-tear is unlikely. If the quality and amount of remaining tissue is poor, re-tear is more likely.

Rare but can occur: The goal of partial meniscectomy is to negate the symptoms of pain, catching and swelling that are common with a torn meniscus. When a portion of meniscus is removed, there is less left to possibly tear again, so it makes sense that retear becomes less likely. A partially respected meniscus, however, may still have remnants of less than normal tissue that can be susceptible to retear.