Which mechanism is most commonly associated with ACL tears?

Which mechanism is most commonly associated with ACL tears?

• A. Direct blow to the knee
• B. External rotation force
• C. Non-impact rotational or hyperextension forces
• D. Varus stress

Answer: (C)

The key idea is that ACL tears are most often non-contact injuries resulting from rotational or hyperextension forces applied to a planted foot. When a person plants the foot and suddenly pivots, cuts, or lands with the knee near full extension, the tibia can translate anteriorly and rotate excessively relative to the femur. This anterior tibial shear combined with rotational stress places the ACL under a surge of strain, leading to rupture even without a direct blow to the knee. That non-contact, rotational or hyperextension mechanism explains why ACL tears frequently occur in sports like basketball, soccer, or skiing during rapid direction changes or awkward landings. Direct blows to the knee can injure other structures or cause different injury patterns, and a purely external rotation force by itself is less likely to produce an ACL tear unless it occurs with the knee in a vulnerable position. Varus stress tends to injure lateral structures such as the lateral collateral ligament, rather than the ACL.

The key idea is that ACL tears are most often non-contact injuries resulting from rotational or hyperextension forces applied to a planted foot. When a person plants the foot and suddenly pivots, cuts, or lands with the knee near full extension, the tibia can translate anteriorly and rotate excessively relative to the femur. This anterior tibial shear combined with rotational stress places the ACL under a surge of strain, leading to rupture even without a direct blow to the knee. That non-contact, rotational or hyperextension mechanism explains why ACL tears frequently occur in sports like basketball, soccer, or skiing during rapid direction changes or awkward landings.

Direct blows to the knee can injure other structures or cause different injury patterns, and a purely external rotation force by itself is less likely to produce an ACL tear unless it occurs with the knee in a vulnerable position. Varus stress tends to injure lateral structures such as the lateral collateral ligament, rather than the ACL.