Anatomy Study Of The Posterolateral Complex Of The Human Knee Joint

Objective: The aim of this study was to observe the anatomy of the posterolateral complex (PLC) of the human knee joint, thus to provide the anatomical foundation for clinical diagnosis and treatment.Methods: 8 knees were selected, except knee joint injury and tumor affection, and the PLC of those knee joints were dissected. The enthesis, the courser and their anatomical relations were identified. The lateral collateral ligament (LCL), popliteal muscle tendon complex and popliteal fibular ligament were measured. The included angle between every tendons and the fibula long axis on different level were calculated and the anti-rotation function of PLC structures were given by the biomechanics mensuration.Results: The PLC of the knee joint includes three-layered structure: the superficial layer is iliotibial tract and biceps tendon. The stratum intermedium include the patella lateral retinaculum, patella-femoris ligament and caput laterale musculi gastrocnemii. The deep layer is made up of lateral joint capsule which insert into marginalis along the lateral meniscus, LCL, popliteal muscle tendon complex, popliteal- fibula ligament, fabella- fibula ligament, arcuate ligaments, posterior cruciate ligament (PCL), meniscus-femur ligament and so on .The iliotibial tract originates from anterior superior iliac spine and insert at Gerdy's tubercle which located at tibia lateral platform. The iliotibial tract is divided into superficial layer, deep layer and capsule-bone layer. Separated the superficial layer may show the deep layer fiber which adhered tightly at epicondylus lateralis femoris and stretch to the bone lateral muscle diastema. The capsule-bone layer started from lateral muscle diastema, gastrocnemius and plantaris post-lateral fascia, stretched to caput breve musculi bicipitis femoris aponeurosis.The biceps femoris descend to the rear of iliotibial tract and has two heads which called the long and short head. The two heads both includes the direct and anterior tendinous. The direct branch of the long and short head added to the LCL which called conjoined tendon and insert at the basilar part of the lateral fibular head. The anterior branch of the short head insert at the tibia superolateral surface combined with the middle one third of lateral capsule. Common perioneal nerve lies in the deep layer of the biceps femoris musculotendinous and has a 1.5 to 2.0cm distance to fibula styloid process.The lateral head of gastrocnemius muscle originates from the LCL rear and coursers from the popliteus muscle tendon. The fabella is a sesamoid which has uncertainty in the lateral head of the gastrocnemius tendon, so the fabella-fibula ligament is has uncertainty. There are 3 in the 8 knees which has fabellae. The patella lateral retinaculum originates from the lateral border of patella and insert on the lateral aspect of the proximal tibia. The patella-femoris ligament which locats at the proximate of the patella lateral retinaculum originates from the lateral border of patella and insert on the condylus lateralis femoris.The LCL originated from lateral tuberositas of the lateral condyles of femur just anterior to the the femoral attachment of the gastrocnemius's lateral head and extends distally, posteriorly over an oblique course to gastrocnemius tendon,below the iliotibial tract ,and end on the lateral aspect of the fibular head by conjoined tendon.The popliteus muscle arises from the posterior medial proximal tibia, extending superiorly and laterally to form a tendon that continues into the joint through the popliteal hiatus, migrations in the lateral condyles of femur and popliteal gully, passes under the LCL, end by inserting on the condylus lateralis femoris tuberositas and form the popliteal muscle tendon complex. The popliteus tendon sends attachments to the lateral meniscus posterior horn (the popliteal meniscal ligament) and to the styloid process of the fibula (the popliteal fibular ligament).The popliteal fibular ligament originates near the popliteus musculotendinous junction and courses distally and laterally to attach to the medial side of the fibular styloid process. This ligament is a short, strong tendinous band that is as wide as or even wider than the popliteus tendon. The arcuate ligament is a thickening part of the articular capsule present Y-shaped structure with medial and lateral limbs, both of which insert distally at the apex of the fibular styloid process just anterior to the fabellofibular ligament. The medial limb extends curvature, over the popliteus muscle and tendon, to merge with the popliteal oblique ligament and the lateral limb extends upright along the joint capsule to the insertion of lateral gastrocnemius femoral condyle and merge with the articular capsule.The PCL originates from the lateral aspect of condylus medialis femoris, courser to the post-lateral, end on the posterior of intercondylar spine of tibia. There is a synovium tissue cover the surface of PCL and the blood vessel passed through it. The PCL and ACL were connected with by a tissue which puffed and fatty at the corner of them. The PCL of the knee joints can be divided into the antero-lateral bundle and the post- internal bundle according to the stop position of ligament fiber.Usually, the meniscus-femur ligament has one or two roots and it originates from the condylus medialis femoris and end on the posterior horn of the lateral meniscus. The name as Humphrey ligament lies at the anterior aspect of PCL and the name as Wrisberg ligament lies at the postero aspect of PCL.Following is the included angle between every main tendons and the fibula long axis on different level: the LCL is about 10°on sagittal plane, the popliteal fibular ligamentis about 29°on coronal plane, the inside articular capsule aspect of popliteal muscle tendon is about 51°on sagittal plane and the outside articular capsule aspect of popliteal muscle tendon is about 44°on coronal plane. Biomechanics test shown,the rotation stability is maintenanced by the different PLC structures of the posterolateral of knee joint and provided mainly by the different PLC structures at different angle of genuflex.Conclusion: The PLC of human knee joint has a complicaed structure which includes three layered parts. The posterior lateral complex including all the structure around the posterolateral aspect of knee joint, but specially describe the posterior lateral corner which including the LCL, the popliteal muscle tendon complex, patella-femoris ligament and the posterolateral articular capsule. Usually, biceps tendon, LCL, popliteus muscle tendon complex and patella-femoris ligament are regarded as the main structure of the posterolateral of the knee joint. In anatomy process we find that each structure of the posterolateral of the knee joint has a intimate relationship and connect with each other into a complete body, thus can play a stable and safe function to the posterolateral of knee joint. Among those the LCL, popliteus tendon complex and popliteal fibular ligament structure are the most important structure unit which form a solid triangle at the posterolateral aspect of the knee joint. This made the knee joint posterolateral has the stable protection function to prevent knee joint inversion, tibia external rotation and fall back. Biomechanics test shown,the rotation stability is provided mainly by the LCL and the popliteal muscle tendon complex and the PCL is the aided structure of anti-external rotation. The rotation stability of the posterolateral of knee joint is provided difference by the different PLC structures at different angle of genuflex.Understanding the characteristic of knee joint posterolateral structure is benefit to make a correct diagnosis of the injury of knee joint PLC by X-ray, CT and MRI, and at the same time can provid anatoomic evidence for repair and reconstitution operation in clinically.