Which sign occurs within 12 hours after ACL injury?

Which sign occurs within 12 hours after ACL injury?

• A. Immediate effusion within 12 hours after injury
• B. Hearing a pop
• C. Sport participation with cutting
• D. MOI deceleration

Answer: (A)

The key idea is that an ACL tear often causes bleeding into the knee (hemarthrosis), which leads to rapid joint swelling. This effusion becomes noticeable within hours after the injury, commonly within the first 12 hours. That makes immediate effusion within 12 hours the most reliable sign to look for after an ACL rupture. Hearing a pop is an event at the moment of injury, not a sign that develops over the next hours. Participating in sports with cutting after the injury is not a sign and reflects activity level, not a clinical sign. The mechanism of injury, such as deceleration, describes how the injury happened rather than something you observe after the fact.

The key idea is that an ACL tear often causes bleeding into the knee (hemarthrosis), which leads to rapid joint swelling. This effusion becomes noticeable within hours after the injury, commonly within the first 12 hours. That makes immediate effusion within 12 hours the most reliable sign to look for after an ACL rupture.

Hearing a pop is an event at the moment of injury, not a sign that develops over the next hours. Participating in sports with cutting after the injury is not a sign and reflects activity level, not a clinical sign. The mechanism of injury, such as deceleration, describes how the injury happened rather than something you observe after the fact.