ACL Deficiency Increases Forces on the Medial Femoral Condyle and the Lateral Meniscus with Applied Rotatory Loads

Area of Science:

• Biomechanics
• Orthopedics
• Sports Medicine

Background:

• The anterior cruciate ligament (ACL) is crucial for knee joint stability.
• Damage to intra-articular structures is common in ACL injuries, but their specific roles in resisting rotatory loads are not fully understood.

Purpose of the Study:

• To investigate the biomechanical impact of ACL deficiency on load distribution within the knee joint.
• To determine how ACL sectioning affects forces on the menisci and articular cartilage under combined valgus and internal rotation torques.

Main Methods:

• Human cadaveric knees were subjected to valgus and internal rotation torques using a robotic manipulator.
• Forces on menisci and femoral condyles were measured with and without a compressive load, before and after ACL sectioning, using the principle of superposition.

Main Results:

• ACL sectioning significantly increased net forces on the lateral meniscus and medial femoral condyle.
• Anterior and lateral shear forces on the lateral meniscus and medial femoral condyle increased substantially after ACL sectioning.
• Minimal changes in forces were observed for the medial meniscus and lateral femoral condyle.

Conclusions:

• ACL deficiency alters knee joint biomechanics, leading to increased loads on specific intra-articular structures.
• These findings provide a biomechanical basis for understanding lateral meniscal injuries and medial compartment alterations associated with ACL insufficiency.