Unhappy triad posterior translation of the tibia on the femur. The classic O'Donoghue triad is characterized by an injury to three knee structures (in order): The anterior cruciate ligament is one of the four crucial ligaments in the knee. It originates from the lateral condyle of the femur and goes to the intercondyloid eminence of the tibia. Its function is to provide stability in the knee and minimize stress across the knee joint. It also restrains excessive forward movement in the leg and limits rotational movements in the knee. Injury An anterior cruciate ligament injury results from excess tension on the ligament.
Tibia malleolus. The lower extremity of the tibia together with the fibula and talus forms the ankle joint. The inferior articular surface is quadrilateral, and smooth for articulation with the talus. It is concave from before backward, broader in front than behind, and traversed from before backward by a slight elevation, separating two depressions. It is continuous with that on the medial malleolus. The anterior surface of the lower extremity is smooth and rounded above, and covered by the tendons of the Extensor muscles; its lower margin presents a rough transverse depression for the attachment of the articular capsule of the