&Meniscal tear=A torn meniscus is a disruption of the articular fibrocartilage located between the femoral condyles and the tibial plateaus. Significant tears lead to loss of smooth motion of the knee (locking), knee effusion, and premature osteoarthritis. Meniscal tears may occur in isolation or in association with a medial collateral ligament (MCL) or anterior cruciate ligament (ACL) tear. Medial meniscal tear is more common than lateral but both may occur together. The most common cause of meniscal injury is a twisting injury with the foot fixed. Older individuals may have degenerative tear with a history of minimal or no trauma. The degree of pain at the time of injury is variable. The acute event is then followed by an insidious onset of pain and swelling over 24 hours. The pain is exacerbated by twisting or pivoting movements. Some patients describe a tearing or popping sensation at the time of injury. Patients with untreated meniscal tears can present weeks after the injury complaining of popping, locking, catching, and the knee "giving out," or may simply report a vague sense that the knee is not moving properly. Effusions are common in patients with meniscal injury, particularly with large or complex tears and tears associated with degenerative arthritis. Patients typically complain of stiffness rather than swelling due to the effusion.