Introduction A diarthrodial joint that allows simultaneous rotation and translation Overview of Knee Ligament Function Ligament Primary function Secondary function Anterior Cruciate Ligament (ACL) Resists anterolateral displacement of the tibia on the femur Resists varus displacement at 0 degrees of flexion Posterior Cruciate Ligament (PCL) Resists posterior tibial displacement, especially at 90 degrees of flexion Resists varus displacement at 0 degrees of flexion Lateral Collateral Ligament (LCL) Resists varus displacement at 30 degrees of flexion Resists posterolateral rotatory displacement with flexion that is less than approximately 50 degrees Popliteofibular Ligament / Posterior Lateral Corner (PLC) Resists posterolateral rotation of the tibia on the femur Resists varus angulation and posterior displacement of the tibia on the femur Medial Collateral Ligament (MCL) Resists valgus angulation Works in concert with ACL to provide restraint toaxial rotation Lateral Structures of Knee Layer 1 Iliotibial tract, biceps femoris Common peroneal nerve lies between layer I and II Layer 2 Patellar retinaculum Layer 3 Superficial: LCL, fabellofibular ligament, ALL Lateral geniculate artery runs between deep and superficial layer Deep: Arcuate ligament, coronary ligament, popliteus tendon, popliteofibular ligament, capsule Medial Structures of Knee Layer 1 Sartorius and fascia (patellar retinaculum) gracilis, semitendinosis, and saphenous nerve run between layer 1 and 2 Layer 2 Semimembranosus, superficial MCL, MPFL, posterior oblique ligament Layer 3 Deep MCL, capsule, coronary ligament ACL Function prevents anterior translation of the tibia relative to the femur Anatomy extrasynovial but intracapsular origin login to view 2 more bullets insertion login to view 2 more bullets structure login to view 10 more bullets Blood supply middle geniculate artery Innervation contains significant innervation by posterior articular branches of tibial nerve contains mechanoreceptors (Ruffini, Pacini, Golgi tendon organs, free-nerve endings) function of innervation login to view 2 more bullets Composition 90% Type I collagen 10% Type III collagen Biomechanics tensile strength login to view 4 more bullets PCL Function prevents posterior translation of the tibia relative to the femur PCL and PLC work in concert to resist posterior translation and posterolateral rotatory instability Anatomy extrasynovial but intracapsular origin login to view 1 more bullet insertion login to view 1 more bullet structure login to view 17 more bullets blood supply login to view 1 more bullet Biomechanics strength: 2500 N (vs posterior translation) LCL (lateral collateral ligament or fibular collateral ligament) Function resists varus angulation works in concert with MCL to provide restraint to axial rotation Anatomy origin login to view 1 more bullet path login to view 1 more bullet insertion login to view 2 more bullets structure login to view 1 more bullet Biomechanics tight in extension and lax in flexion strength: 750 N (vs varus stress) PLC (posterolateral corner) Function works synergistically with the PCL to control external rotation and posterior translation Anatomy included structures login to view 4 more bullets variable login to view 3 more bullets MCL Function resists valgus angulation works in concert with ACL to provide restraint to axial rotation Anatomy origin login to view 1 more bullet structure login to view 12 more bullets Biomechanics strength: 4000 N (vs valgus stress) Posteromedial corner Function important for rotatory stability Anatomy lies deep to MCL formed by login to view 5 more bullets Medial patellofemoral ligament (MPFL) Function provide restraint against lateral translation of the patella from 0° to 30° of knee flexion Characteristics low tension throughout flexion-extension (2-10N of force) isometric between 0° and 90°, then becomes slack beyond 90° can withstand 200N before tearing login to view 1 more bullet Anatomy lies in 2nd layer of medial soft tissue complex 2 bundles login to view 2 more bullets femoral insertion login to view 5 more bullets patellar attachment login to view 1 more bullet Pathoanatomy tears off femoral attachment > patellar attachment login to view 1 more bullet risk of 2nd dislocation is 13% login to view 1 more bullet Anterolateral Ligament Function rotational stability Anatomy lies in Layer 3 with LCL characteristics login to view 4 more bullets attachments login to view 4 more bullets attachments to middle third of lateral meniscus body login to view 2 more bullets lateral inferior genicular artery and vein contained between lateral meniscus and ALL at level of joint line NO connections to ITB Pathoanatomy Segond's fracture (associated with ACL rupture) is avulsion fracture of ALL