University:
Kentucky State University
Course:
BIO 301 | Human Anatomy
Academic year:

2020
Views:

263

Pages:

43
Author:

crawniadxfo

Knee Joint Knee joint Articulating surfaces: Knee joint is the largest synovial joint in the body. Consists of two joints: Articulation between the femur and tibia (weight- bearing) Articulation between the patella and patellar surface of femur Quadriceps tendon Allows the pull of quadriceps femoris to be directed anteriorly over the knee to the tibia without tendon wear Patellar ligament Type: Tibiofemoral joint Modified synovial hinge (bicondylar) Allows flexion and extension with some degree of medial and lateral rotation Patellofemoral joint Plane gliding joint Capsule: The capsule is attached to the margins of the articular surfaces and surrounds the sides and posterior aspect of the joint. On the front of the joint, the capsule is absent. The capsule is completed anteriorly by patella, ligamentum patellae, medial and lateral patellar retinacula Posterior view of the knee On each side of the patella, the capsule is completed anteriorly by expansions from the tendons of vastus lateralis and medialis forming Medial and Lateral patellar retinacula The ligamentum patellae is attached above to the lower border of the patella and below to the tuberosity of the tibia. Lateral patellar retinaculum Medial patellar retinaculum Patellar ligament Ligaments: The ligaments may be divided into those that lie outside the capsule (extracapsular) and those that lie within the capsule (intracapsular) Extracapsular ligaments: Ligamentum patellae Lateral collateral ligament Medial collateral ligament Oblique popliteal ligament Intracapsular Ligaments (within the joint cavity): Anterior Cruciate Ligament Posterior Cruciate Ligament The lateral collateral ligament is cordlike and is attached above to the lateral femoral epicondyle and below to the head of the fibula. The medial collateral ligament is a flat band and is attached above to the medial femoral epicondyle and below to the upper medial surface of tibia. Why??? The tendon of the popliteus muscle intervenes between the ligament and the lateral meniscus An opening in the capsule permits the tendon of the popliteus to emerge The popliteus tendon passes between the lateral meniscus and the capsule What does this mean?? Posterior view of the knee Semimembranous The oblique popliteal ligament is a tendinous expansion derived from the semimembranosus muscle. It strengthens the posterior aspect of the capsule Cruciate: latin for shaped like a cross Anterior Cruciate Ligament Posterior Cruciate Ligament The cruciate ligaments are named anterior and posterior, according to their tibial attachments Are the main bond between the femur and the tibia throughout the joint's range of movement Anterior view of the knee The anterior cruciate ligament is attached to the anterior intercondylar area of the tibia and passes upward, backward, and laterally, to be attached to the posterior part of the lateral wall of intercondylar fossa The anterior cruciate ligament restricts anterior displacement of the tibia relative to the femur The posterior cruciate ligament is attached to the posterior intercondylar area of the tibia and passes upward, forward, and medially to be attached to the anterior part of the medial wall of intercondylar fossa The anterior cruciate ligament restricts posterior displacement of the tibia relative to the femur The tests for the integrity of the cruciate ligaments are the anterior and posterior drawer signs Tearing of the anterior cruciate ligament allows the tibia to be easily pulled forward (anterior drawer sign) Test anterior cruciate ligament Ruptured ACL Tearing of the posterior cruciate ligament allows the tibia to be easily pulled posteriorly (posterior drawer sign) Test posterior cruciate ligament Ruptured PCL Menisci  Are medial and lateral Cshaped fibrocartilages  The upper surfaces are in contact with femoral condyles The lower surfaces are in contact with tibial condyles.  Their function is to deepen the articular surfaces of the tibial condyles to receive the convex femoral condyles; they also serve as cushions between the two bones Each meniscus is attached to the upper surface of the tibia by anterior and posterior horns Superior view of the proximal end of Tibia Medial collateral ligament Medial meniscus The medial meniscus is attached to the capsule of the knee joint and the medial collateral ligament, it is relatively immobile Note The lateral condyle of femur is a bit longer than the medial Helps in preventing the lateral dislocation of patella Articularis genu Synovial Membrane The synovial membrane lines the capsule The synovial membrane of the knee joint forms pouches (bursae) To provide low-friction surfaces for the movement of tendons associated with the joint Some bursae communicate with the joint cavity and some do not normally communicate For example On the front and above the joint, it forms a pouch, which extends up beneath the quadriceps femoris for three fingerbreadths above the patella, forming the suprapatellar bursa. This is held in position by the attachment of the articularis genu muscle Note: Suprapatellar bursa communicates with the joint cavity Note: Suprapatellar bursa Consequently, abrasions or penetrating wounds (e.g stab wounds) superior to the patella may result in suprapatellar bursitis caused by bacteria entering the bursa from the torn skin. The infection may spread to the knee joint Prepatellar bursa The prepatellar bursa lies in the subcutaneous tissue between the skin and the patella Prepatellar bursitis (housemaid’s knee) Is usually a friction bursitis caused by friction between the skin and patella Subcutaneous infrapatellar bursa The superficial infrapatellar bursa lies in the subcutaneous tissue between the skin and the ligamentum patellae Subcutaneous infrapatellar bursitis results from excessive friction between the skin and tibial tuberosity Deep infrapatellar bursa The deep infrapatellar bursa lies between the ligamentum patellae and the tibia Infrapatellar fat pad Bursae are found wherever skin, muscle, or tendon rubs against bone. Four are situated in front of the joint and the rest are found behind the joint Subtendinous bursa of biceps femoris Anserinus bursa The other bursae are found related to the tendon of insertion of the biceps femoris; related to the tendons of the sartorius, gracilis, and semitendinosus muscles as they pass to their insertion on the tibia; beneath the lateral head of origin of the gastrocnemius muscle; and beneath the medial head of origin of the gastrocnemius muscle, beneath thhe iliotibial tract The popliteal bursa is found between the tendon of popliteus and the lateral condyle of tibia and communicates with the joint cavity. The cruciate ligaments lie behind the synovial cavity and are not bathed in synovial fluid. Locking mechanism When standing the knee joint is locked into position, thereby reducing the amount of muscle work needed to maintain the standing position Locking mechanism has 3 components: 1- The change in the shape and size of the femoral articular surfaces 2- The medial rotation of the femur on the tibia during extension Medial rotation and full extension tightens all the associated ligaments 3- The body’s center of gravity is positioned along vertical line that passes anterior to the knee joint Keeps the knee extended when standing Note The joint surfaces become larger and more stable in extension The extended knee is said to be in the locked position Before flexion of the knee can occur, it is essential that the major ligaments Be untwisted/ slackened to permit movements between the joint surfaces This unlocking or untwisting process is accomplished by the popliteus muscle Which laterally rotates the femur on tibia The knee joint can not be flexed unless it is unlocked by the popletius Popliteus Origin: lateral surface of lateral condyle of femur by a rounded tendon Insertion: posterior surface of tibia above soleal line Nerve supply: Tibial nerve Action: flexes leg at knee joint, unlocks the extended knee at the initiation of flexion by lateral rotation of femur on tibia (when the foot is on the ground) and slackens ligaments of knee joint Medial rotates the tibia on the femur Unlocking means Lateral rotation of the femur Or Medial rotation of the tibia Locking means………….. rotation of the femur Or …………rotation of the tibia Note The popliteus arises within the knee joint Its tendon separates the lateral meniscus from the lateral collateral ligament and the capsule It emerges through the lower part of the posterior surface of the capsule to pass to its insertion Movements of the knee joint Flexion Biceps femoris, Semitendinosus, and Semimembranosus muscles, assisted by Gracilis and Sartorius muscles Flexion is limited by the contact of the back of the leg with the thigh Extension Quadriceps femoris Extension is limited by the tension of all the major ligaments of the joint. Medial Rotation Sartorius, Gracilis, and Semitendinosus Lateral Rotation Biceps femoris The stability of the knee joint depends on the tone of the strong muscles acting on the joint and the strength of the ligaments. Of these factors, the tone of the muscles is the most important, and it is the job of the physiotherapist to build up the strength of these muscles, especially the quadriceps femoris, after injury to the knee joint. Nerve supply of the knee joint Femoral, obturator, common fibular and tibial nerves Blood supply of the knee joint Femoral, popliteal, lateral circumflex femoral arteries The medial collateral ligament is firmly attached to the capsule and medial meniscus Tibial collateral ligament extends from medial epicondyle of femur to medial aspect of tibia The tibial collateral ligament prevents lateral displacement (abduction) of tibia under femur The 3 most commonly injured structures at the knee are: Tibial collateral ligament Medial meniscus ACL The terrible or Unhappy triad Usually results from a blow to the lateral aspect of the knee with the foot on the ground Knee joint and menisci from above ACL and PCL attachment points Prepatellar bursitis (housemaid’s knee) Lateral collateral ligament: isolated from knee joint Note: it is cord-like Medial collateral ligament: isolated from knee joint Note: it is flat Patellar tendon rupture: Sagittal radiograph Quadriceps tendon Femur Suprapatellar bursa Lateral meniscus Patella Tibia Patellar ligament Fibula MRI of the Knee (Sagittal View) Femur PCL Lateral meniscus ACL Medial meniscus Tibia MRI of the Knee (Coronal View)

Knee Joint

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