The Knee Tibio Femoral Osteology Distal Femur with Proximal Tibia Largest Joint Cavity in the Body A modified hinge joint with significant passive rotation Technically one degree of freedom Flexion Extension but passive rotary component is essential Unites the two longest levers in the body Tibio Femoral Support Knee supports the weight of the body and transmits forces from the ground Functional stability of the joint is derived from the passive restraint of the ligaments the active support of muscles the joint geometry and the compressive forces pushing the bones together Menisci The surface of the tibia is covered by fibrocartilaginous menisci They Enhance the joint stability by deepening the contact surface They help with shock absorption by transmitting of weight bearing load in full extension and some in flexion as well They protect the articular cartilage They transmit the load across the surface of the joint thus reducing the load per unit area on the tibio femoral contact sites The contact area in the joint is reduced 50 when the menisci are absent Menisci Menisci In hi load situations 70 of the load is absorbed by the menisci especially the lateral meniscus The menisci assist in lubrication of the joint by acting as a space filling mechanism more fluid is dispersed to the surface of tibia and femur 20 increase in friction following meniscal removal Medial Meniscus larger reflects the shape of medial tibial condyle A P horns attached to medial collateral ligament and basically immobile Lateral Meniscus smaller tighter almost a complete circle A P horns NOT attached to lateral collateral ligament Menisci Attached via Transverse ligament anteriorly Fibrous bands connecting the anterior horns of both menisci to the medial and lateral retinaculum sometimes called the meniscopatellar fibers or ligaments The medial collateral ligament attaches to the medial meniscus The tendon of semimenbranosis sends fibers to the posterior edge of medial meniscus The popliteus muscle sends fibers to the lateral meniscus The meniscofemoral ligament extends from the lateral meniscus post to the inside of the medial condyle near the PCL The coronary liagaments AKA meniscotibial Menisci Menisci Meniscal Attachments Coronary Ligaments Patellomeniscal Ligament Menisci Menisci Joint Capsule Largest in body Surrounds entire joint except anteriorly Originally in utero is three capsule that merge into one MCL flat band attached above medial condyle of the femur and below to the medial surface of the shaft of the tibia resists lateral displacement LCL cordlike attached above the lateral condyle of femur and below the head of the fibula resists medial displacement Capsule Collaterals Collaterals Capsule Oblique Popliteal derived from semimembranosus on posterior aspect of the capsule runs from that tendon to medial aspect of the lateral femoral condyle posteriorly Arcuate popliteal from head of fibula runs over the popliteus muscle to attach into posterior joint capsule Posterior Capsule Posterior Capsule Little Guys Capsule Cruciates called intrinsic note synovium ACL attached to the anteriorly intercondylar area of the tibia and passes upward backward and laterally to be attached to the posterior part of medial surface of the lateral femoral condyle ACL fibers run in three directions anteromedial intermediate and posterolateral directions NWB this ligament prevents anterior displacement of tibia on femur Cruciates Cruciates Cruciates Cruciates Capsule PCL attached to the posterior intercondylar area of the tibia and passes upward forward and medially to be attached to the anterior part of the lateral surface of the medial femoral condyle PCL fibers run in two directions anteromedial and posterolateral directions NWB prevents posterior displacement of tibia on femur In closed chain the role of cruciates changes Pes Anserine Unholy Triad ACL MCL Medial Meniscus Mechanism of injury generally involves all three at same time Compartments of the Knee Medial Medial retinaculum Pes anserine Adductor Magnus Semimenbranosus Capsular ligaments meniscofemoral meniscotibial post Oblique MCL PCL Compartments Lateral Lateral Retinaculum IT Band Biceps Attachment Popliteus MM LCL Lateral capsular ligaments meniscofemoral meniscotibial Arcuate ligament ACL Arcuate Lig Post Lateral Capsule LCL Called Arcuate Complex Patello Femoral Joint Patella with ant and distal femur so called trochlear groove Patella is a sesamoid bone imbedded in the quadriceps mechanism tendon attachment continuing on to patellar ligament to tibial tuberosity Purposes Increase the leverage or torque of quads by increasing distance from the axis of motion Provide bony protection to distal joint surface of femoral condyles when knee is flexed Prevent damaging compression forces on the quadriceps tendon with resisted knee flexion such as squats Patello Femoral Joint Patella Posterior surface covered with articular cartilage Thickest articular cartilage in body Facets Medial side had medial facet and the odd facet Lateral side has lateral facet Separated by vertical ridge Can divide med and lat facets to superior and inferior Proximal part called the base distal part the pole or apex Patella Patella Quads stabilize patella on all sides and guide motion between patella and femur Distally the patella is anchored by the patellar ligament Retinaculum anchor patella on each side VMO contributes on medial side IT band and VL assist laterally Patella Patella Patella Patella Patella From full flexion to extension the patella slides 7 to 8 cm During the beginning of flexion the contact is on the distal patella As flexion approaches 90 degrees the articulating surface moves towards the base to cover the proximal one half of the patella At 135 degrees of flexion the odd facet comes into contact Patella The odd facet is frequently the 1st part of patella to be affected in premature degeneration of articular cartilage The load on the patella differs according to activity In walking 1 3 body weight Climbing stairs 3 to 4 X body weight Squatting without weight 7 to 8 X body weight Q Angle An angle found by drawing a line from ASIS to middle of patella and a second line from mid patella to tibial tuberosity Represents efficiency of Quads Most efficient 10 degrees Males range from 10 14 Females from 15 17 Represents the valgus stress acting on knee and if excessive can cause patello femoral problems Great than 17 degrees considered excessive called Genu Valgum or