A. Knee

B. ankle

Correct answer: a

Meniscus is a C-shaped cushioning structure composed of elastic cartilage, which is located between the two main bones that make up the knee joint. Meniscus can play a buffering role, thus preventing articular cartilage from being damaged by impact. Meniscus injury can be caused by trauma or degeneration. Meniscus injury caused by severe trauma can be complicated with knee joint soft tissue injury, such as lateral collateral ligament injury, cruciate ligament injury, joint capsule injury, cartilage surface injury and so on. This is often the cause of swelling after injury.