Biomechanics of Knee Joint PDF

Biomechanics of knee joint DR.Mennat-Allah ali  Type of knee joint Hinge joint………OR……Modified Hinge? WHY??? more precisely a combination of hinge and pivot joints and is sometimes called a modified hinge joint So, knee is Modified hinge The kne...

Biomechanics of knee joint DR.Mennat-Allah ali  Type of knee joint Hinge joint………OR……Modified Hinge? WHY??? more precisely a combination of hinge and pivot joints and is sometimes called a modified hinge joint So, knee is Modified hinge The knee is capable of rotation and translation about three axes and therefore has six degrees of freedom osteology Proximal tibia contains the tibial plateaus with their articular facets. Concav e Concav e The medial articular facet is concave from medial to lateral and from ANT to post convex The lateral articular facet is concave medial to lateral but slightly convex anterior to posterior. 20° of lateral rotation as the knee moves from full extension to at least 90° of 3D motion in closed flexion kinematic chain femoral abduction with respect to the tibia with knee flexion is much smaller The timing of the medial or lateral rotation there is an initial rotation at the beginning of flexion (or end of extension), which then ceases until at least 45° of flexion. Others suggest that the rotation continues smoothly through at least the first 90° of In closed kinematic chain During knee flexion in a closed chain, the femur rolls backward while the tibia rotates forward. During knee extension in a closed chain, the femur rolls forward while the tibia rotates backward. Arthrokinematics During flexion the lateral femoral condyle translates posteriorly The medial femoral condyle translates forwards about 4 mm between 10° and 45° flexion. The anterior-posterior gliding that is limited by the cruciate ligaments  Tibio-Femoral angle Plane Frontal Between 2 1- Anatomical axis of the lines femur. 2- Anatomical axis of the tibia. Value 170°-175°Laterally. Function Determine normal physiological knee valgus. Abnormal ↑↑ Genu varum (Bow change leg) ↓↓ Genu valgum (Knock knees) Abnormal Tibio-Femoral angle Structure of the knee joint 3- Menisci of knee joint Structure of the knee joint 3- Menisci of knee joint Function of the menisci Motion of the menisci The menisci glide posteriorly with knee flexion and anteriorly with knee extension Why? The menisci move in concert with the rolling femoral condyles As the femur rolls posteriorly in knee flexion, the menisci are pushed posteriorly ahead of the rolling condyles. Similarly, they glide anteriorly ahead of the anteriorly rolling condyles during knee extension. The screw home mechanism The screw home mechanism describes the final medial rotation of the femur as the knee reaches full extension. The tibiofemoral movement during knee flexion and extension exhibits characteristic components: 1. During flexion, as the femur rolls into flexion, it rotates laterally with respect to the tibia. 2. Conversely, the femur rotates medially as it rolls into extension. Contact between the femur and tibia migrates posteriorly on the tibia during flexion and anteriorly during extension. Structure of the knee joint 4- Ligaments of the knee joint Structure of the knee joint 4- Ligaments of the knee joint  Quadriceps (Q) angle Angle lines First: line from ASIS to the midpoint of the patella. Second: line connecting the tibial tuberosity with the midpoint of the patella. Function Determine line of force of Quadriceps muscle  The ridge on the posterior surface of the patella glides in the Patelofemoral joint reciprocal groove, or sulcus, on the anterior surface of the distal femur The patellofemoral joint is a gliding joint.  Functions of patella Although the patella protects the quadriceps tendon from excessive friction from the femur during knee flexion, Its primary function is to increase the angle of application and, consequently, the moment arm of the quadriceps tendon.  Clinical note Without the patella: the extensor muscle is functionally longer and unable to shorten adequately to extend the knee through its entire excursion Thus the quadriceps exhibits active insufficiency, which in the knee is referred to as an extensor lag (describes the lack of full knee extension with full contraction of the quadriceps What is the functional importance of Patellofemoral Motion?? The large changes in contact location and area between the femur and patella produce large changes in stress (force/area). It is believed that abnormal stresses contribute to patellofemoral joint dysfunction  Patello-femoral joint reaction force Throughout range of knee flex. and ext. Motion of patella during flexion and extention Patello-femoral Kinetics Patellar Malalignment causes patella Alta : is the condition where people are born with a kneecap (patella) positioned higher in the front of the knee than the average. Congenital Defect: This defect is acquired during the development of the embryo. Under this condition, a person has had patella Alta conditions since its birth. Injuries of the Knee can cause patella Alta. This might be a primary cause for the patella Alta’s medical condition as various strenuous activities like sports can set the kneecap out. Patella Baja Quadriceps Dysfunction: Poliomyelitis Bony Or Ligamentous Trauma: Fractures Osteotomies Tibial Tubercle Transplant ACL Repair Total Knee Replacement: Seen In 25% Of Patients Line of gravity It also is important to recognize that many activities in the erect posture that require knee flexion such as descending stairs and sitting down use the quadriceps femoris to control the flexion rather than the hamstrings to produce the flexion. The weight of the head, arms, and trunk creates an external flexion moment at the knee that is resisted by an internal extension moment generated by the quadriceps femoris muscle EFFECT OF CHAIR HEIGHT ON FUNCTIONALLY IMPAIRED ELDERLY INDIVIDUALS More quadriceps force is required to rise from a low chair than from a higher chair Tightness of hamstring Post pelvic tilting Flatten of lumber Meniscus When a bucket-handle tear of the medial meniscus was removed, the application of joint load caused the tibia to displace (subluxate) forward on the femur, thereby changing the balance condition of the knee. Knee pathomechanics ❖ Genu recurvatum. Thank u