Lecture 09. Joints of the Lower Limb,

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Learning Objectives

• Describe the basic structure of a synovial joint (joint capsule, articular cartilage, synovial membrane)
• Explain extracapsular vs capsular vs intracapsular ligaments
• Describe the major ligamentous support for the hip / knee /ankle
• Explain function of lower extremity ligaments with regards to standing at rest
• Understand common injuries and explain anatomical basis for basic diagnostic tests

True/False Questions

1. Standing at rest is very metabolically efficient because ligaments, not muscles, counteract the force of gravity at the hip and knee joints.
2. A valgus force applied to the knee will stress the lateral collateral ligament.
3. The ACL prevents posterior displacement of the femur with respect to the tibia
4. When approaching full knee extension, the femur rotates internally slightly with respect to the tibia, resulting in locking of the knee joint.
5. When the knee is fully extended, contraction of the popliteus muscle causes internal rotation of the femur with respect to the tibia which unlocks the knee joint.

Essay Questions

1. Essay Question #1: An 18 year old football player is tackled during a football game. He falls to the ground holding his left knee. When reviewing the video replay of the tackle, it is noted that he was struck on the posterior lateral aspect of the knee. On exam, he has a positive anterior drawer sign (forward sliding of tibia) and tenderness and laxity (relaxation/looseness) of the medial joint space of the knee when valgus stress is placed on it. Discuss the anatomy of the knee joint with regards to this injury. Explain the normal anatomy of bones, cartilage, and ligaments. Discuss the anterior drawer sign and what a positive finding indicates. Explain what the finding of laxity during a valgus stress test indicates. What structures are likely injured?
2. Essay Question #2: The passenger of a sports car was thrown forward during an acute deceleration. A posterior dislocation of the hip joint was confirmed by a radiologic study. Discuss the anatomy of the hip joint with regards to this injury. Explain the normal anatomy of bones, cartilage, and ligaments. What structures are likely injured?