The Biomechanics of the Human Lower Extremity Chapter 8 The Biomechanics of the Human Lower Extremity Basic Biomechanics, 7th edition By Susan J. Hall, Ph.D. © 2014 The McGraw-Hill Companies, Inc. All rights reserved. McGraw-Hill/Irwin

Basic Biomechanics, 7th edition Structure of the Hip What is the hip joint? A ball and socket joint where the head of the femur articulates with the concave acetabulum More stable than the shoulder because of bone structure and the number and strength of the muscles and ligaments crossing the joint Basic Biomechanics, 7th edition By Susan J. Hall, Ph.D.

Ischiofemoral ligament Structure of the Hip Iliofemoral (Y) ligament Pubofemoral ligament Femur Ischium Anterior view Iliofemoral ligament Ischiofemoral ligament Posterior view The integrity of the hip is enhanced by the strong ligaments crossing the joint. Basic Biomechanics, 7th edition By Susan J. Hall, Ph.D.

Basic Biomechanics, 7th edition Structure of the Hip Femoral head Femur Acetabulum Ilium Sacrum Pubis Ischium The pelvic girdle includes the two ilia and the sacrum. It can be rotated forward, backward, and laterally to optimize positioning of the hip. Basic Biomechanics, 7th edition By Susan J. Hall, Ph.D.

Basic Biomechanics, 7th edition Movements at the Hip What movements of the femur are facilitated by pelvic tilt? Pelvic tilt direction Femoral movement Posterior Flexion Anterior Extension Lateral (to opposite Abduction side) Basic Biomechanics, 7th edition By Susan J. Hall, Ph.D.

Basic Biomechanics, 7th edition Movements at the Hip Flexor muscles at the hip are iliacus and psoas major, assisted by pectineus, rectus femoris, sartorius, and tensor fascia latae. Basic Biomechanics, 7th edition By Susan J. Hall, Ph.D.

Basic Biomechanics, 7th edition Movements at the Hip Extensor muscles at the hip are gluteus maximus and the hamstrings: biceps femoris, semimembranosus, and semitendinosus. Basic Biomechanics, 7th edition By Susan J. Hall, Ph.D.

Basic Biomechanics, 7th edition Movements at the Hip The abductor muscle at the hip is the gluteus medius, assisted by gulteus minimus. Basic Biomechanics, 7th edition By Susan J. Hall, Ph.D.

Basic Biomechanics, 7th edition Movements at the Hip The adductor muscles at the hip are adductor magnus, adductor longus, and adductor brevis, assisted by gracilis. Basic Biomechanics, 7th edition By Susan J. Hall, Ph.D.

Basic Biomechanics, 7th edition Loads on the Hip The major loads acting on the hip during stance include the weight of body segments above the hip (wt), tension in the hip abductor muscles (Fm), and the joint reaction force (R) generated in accordance with Newton’s third law. wt Fm R The hip is a major weight-bearing joint that is never fully unloaded during daily activities. In addition to body weight, the tension in the large, strong hip muscles further adds to compression at the joint. Basic Biomechanics, 7th edition By Susan J. Hall, Ph.D.

Basic Biomechanics, 7th edition Structure of the Knee What is the tibiofemoral joint? Dual condyloid articulations between the medial and lateral condyles of the tibia and the femur; composing the main hinge joint of the knee Considered to be the knee joint Basic Biomechanics, 7th edition By Susan J. Hall, Ph.D.

What is the patellofemoral joint? Structure of the Knee What is the patellofemoral joint? Femur Articulation between the patella and the femur (The patella improves the mechanical advantage of the knee extensors by as much as 50%) Basic Biomechanics, 7th edition By Susan J. Hall, Ph.D.

Basic Biomechanics, 7th edition Structure of the Knee What are the menisci? Cartilaginous discs located between the tibial and femoral condyles Structures that distribute the load at the knee over a large surface area and also help absorb shock Basic Biomechanics, 7th edition By Susan J. Hall, Ph.D.

Basic Biomechanics, 7th edition Structure of the Knee The menisci of the knee. Basic Biomechanics, 7th edition By Susan J. Hall, Ph.D.

Basic Biomechanics, 7th edition Structure of the Knee What major ligaments cross the knee? Lateral Medial collateral ligament Posterior view Collateral ligaments: cross the medial and lateral aspects of the knee. Cruciate ligaments: cross each other in connecting the anterior and posterior aspects of the knee. Basic Biomechanics, 7th edition By Susan J. Hall, Ph.D.

Basic Biomechanics, 7th edition Movements at the Knee The popliteus “unlocks” the fully extended knee by laterally rotating the femur with respect to the tibia to allow flexion to proceed. Basic Biomechanics, 7th edition By Susan J. Hall, Ph.D.

Basic Biomechanics, 7th edition Movements at the Knee What muscles contribute to flexion at the knee? Biceps femoris Semitendinosus Semimembranosus (The hamstrings, assisted by: gracilis, sartorius, popliteus, and gastrocnemius.) Basic Biomechanics, 7th edition By Susan J. Hall, Ph.D.

Basic Biomechanics, 7th edition Movements at the Knee What muscles contribute to extension at the knee? Vastus lateralis Vastus intermedius Vastus medialis (deep to Rectus femoris) Rectus femoris (The quadriceps muscles.) Basic Biomechanics, 7th edition By Susan J. Hall, Ph.D.

Basic Biomechanics, 7th edition Loads at the Knee Fm C Ft Compression at the patellofemoral joint is the vector sum of tension in the quadriceps (Fm) and the patellar tendon (Ft). With increased flexion at the knee, compression increases because of the changed orientation of the force vectors and increased tension requirement in the quadriceps to maintain body position. Basic Biomechanics, 7th edition By Susan J. Hall, Ph.D.

Basic Biomechanics, 7th edition Structure of the Ankle Where is the tibiotalar joint? Hinge joint where the convex surface of the superior talus articulates with the concave surface of the distal tibia Considered to be the ankle joint Tibia Talus Basic Biomechanics, 7th edition By Susan J. Hall, Ph.D.

Basic Biomechanics, 7th edition Structure of the Ankle Where is the distal tibiofibular joint? Tibia Fibula (A syndesmosis where dense, fibrous tissue binds the distal tibia and fibula together) Basic Biomechanics, 7th edition By Susan J. Hall, Ph.D.

The bony structure of the ankle. Fibula Tibia Talus Calcaneus Posterior view The bony structure of the ankle. Basic Biomechanics, 7th edition By Susan J. Hall, Ph.D.

Basic Biomechanics, 7th edition Movements at the Ankle Dorsiflexors at the ankle include tibialis anterior, extensor digitorum longus, and peroneus tertius, assisted by extensor hallucis longus. Basic Biomechanics, 7th edition By Susan J. Hall, Ph.D.

Basic Biomechanics, 7th edition Movements at the Ankle Plantar flexors at the ankle are gastrocnemius and soleus, assisted by tibialis posterior, plantaris, peroneus longus, flexor hallucis longus, peroneus brevis, and flexor digitorum longus. Basic Biomechanics, 7th edition By Susan J. Hall, Ph.D.

Basic Biomechanics, 7th edition Structure of the Foot Where is the subtalar joint? Calcaneus Talus (The anterior and posterior facets of the talus articulate with the sustencalculum tali on the superior calcaneus) Basic Biomechanics, 7th edition By Susan J. Hall, Ph.D.

Basic Biomechanics, 7th edition Structure of the Foot Where are the tarsometatarsal and intermetatarsal joints? Metatarsals Tarsals Intermetatarsal joints Tarsometatarsal joints Nonaxial joints that permit only gliding movements Enable the foot to function as a semi-rigid unit and to adapt flexibly to uneven surfaces during weight bearing Basic Biomechanics, 7th edition By Susan J. Hall, Ph.D.

Basic Biomechanics, 7th edition Structure of the Foot Where are the metatarsophalangeal and interphalangeal joints? Metatarsals Phalanges Metatarsophalangeal joints Interphalangeal joints Condyloid and hinge joints, respectively The toes function to smooth the weight shift to the opposite foot during walking and help maintain stability during weight bearing by pressing against the ground when necessary Basic Biomechanics, 7th edition By Susan J. Hall, Ph.D.

Basic Biomechanics, 7th edition Structure of the Foot What are the plantar arches? The medial and lateral longitudinal arches stretch from the calcaneus to the metatarsals and tarsals The transverse arch is formed by the bases of the metatarsal bones Basic Biomechanics, 7th edition By Susan J. Hall, Ph.D.

Basic Biomechanics, 7th edition Structure of the Foot What are the plantar fascia? Lateral view Plantar view Plantar fascia Thick bands of fascia that cover the plantar aspects of the foot During weight bearing, mechanical energy is stored in the stretched ligaments, tendons, and plantar fascia of the foot. This energy is released to assist with push-off of the foot from the surface. Basic Biomechanics, 7th edition By Susan J. Hall, Ph.D.

Basic Biomechanics, 7th edition Movements of the Foot What muscles are responsible for toe flexion and extension? Flexion - flexor digitorum longus, flexor digitorum brevis, quadratus plantae, lumbricals, interossei Extension - extensor hallucis longus, extensor digitorum longus, extensor digitorum brevis Basic Biomechanics, 7th edition By Susan J. Hall, Ph.D.

Basic Biomechanics, 7th edition Movements of the Foot What muscles are responsible for inversion and eversion? Inversion - tibialis posterior, tibialis anterior Eversion - peroneus longus, peroneus brevis, assisted by peroneus tertius Basic Biomechanics, 7th edition By Susan J. Hall, Ph.D.