The stretch or tear of a ligament at the knee joint. Sprains are usually characterized in three different severities:· Grade 1-A stretch to the ligament with a few micro tears. · Grade 2-When you actually tear some fibers. Surgery may be required. · Grade 3-Either significant tears or a complete rupture. Surgery is usually the prognosis.

a joint injury that causes a

an injury of the ligaments, the tough bands of fibrous tissue that connect the bones of the upper and lower leg at the knee joint