A peel-off injury refers to a tearing away of the posterior cruciate ligament (PCL) from the tibia (lower leg bone), one of the places where it attaches. The posterior cruciate ligament is one of two ligaments that criss-cross to form an X-shape inside the knee.
Together, these ligaments hold the knee stable and keep the bones from shifting too far apart. The posterior cruciate ligament is designed to prevent the tibia from sliding too far back underneath the femur (thigh bone).
The word “peel-off” refers to the fact that the ligament litreally pulls clean away from the bone where it normally attaches. Another term for this type of injury is tibial avulsion of the PCL. Trauma from sports injuries or falls is the main mechanism leading to a peel-off injury of the PCL. Although adults can have this injury, most cases occur in boys between the ages of 12 and 13.
A direct blow to the upper portion of the tibia (just below the knee) while the knee is bent can cause a peel-off injury. Most of these injuries occur during sports participation (e.g., soccer, basketball, dodge ball) or as a result of a fall.