An ACL tear refers to an injury to the anterior cruciate ligament, a key ligament in the knee that helps stabilize the joint. This injury often occurs during sports activities that involve sudden stops, jumps, or changes in direction. Symptoms typically include pain, swelling, and a feeling of instability in the knee. Diagnosis of an ACL tear usually involves a physical examination and imaging tests like an MRI. Treatment options vary based on the severity of the tear and may include rest, physical therapy, or surgery. Rehabilitation is essential for restoring strength and function to the knee after an ACL tear.