The Biomechanics of the Human Lower Extremity Prepared by Yassr Y. Kahtan Based upon TK Koesterer, Ph.D., ATCHumboldt State University Objectives Explain how anatomical structure affects movement capabilities of lower extremity articulations. Identify factors influencing the relative mobility and stability of lower extremity articulations. Explain the ways in which the lower extremity is adapted to its weightbearing function. Identify muscles that are active during specific lower extremity movements. Structure of the Hip Anterior reinforcement from iliofemoral ligament and pubofemoral ligament Posterior reinforcement from ischiofemoral ligament. Iliopsoas Bursa Deep Trochanteric Bursa Femur major weightbearing bone − Longest, largest and strongest in body. Movements at the Hip Pelvic Girdle Flexion Extension Abduction Adduction Medial and Lateral Rotation of Femur Horizontal Abduction and Adduction Loads on the Hip During swing phase of walking: − Compression on hip approx. same as body weight (due to muscle tension) Increases with hard-soled shoes Increases with gait increases (both support and swing phase) Body weight, impact forces translated upward thru skeleton from feet and muscle tension contribute to compressive load on hip. Structure of the Knee A large synovial joint with three articulations within joint capsule. Tibiofemoral Joint Menisci Ligaments: tibial and fibular collateral, anterior and posterior cruciate, iliotibial band Patellofemoral Joint Joint Capsule and Bursae Movements at the Knee Flexion and Extension −Popliteus −Quadriceps Rotation and Passive Abduction and Adduction Patellofemoral Joint Motion Loads on the Knee Forces at tibiofemoral Joint − Loaded with shear and compression forces during daily activities. − Medial tibial plateau Forces at Patellofemoral Joint − With a squat, reaction force is 7.6 times BW on this joint. − Beneficial to rehab of cruciate ligament or patellofemoral surgery Structure of the Ankle Movements of the ankle: −Dorsiflexion: −Tibialis anterior −Extensor digitorum longus −Peroneus tertius −Plantar Flexion: −Two heads of gastrocnemius −Soleus Structure of the Foot Subtalar Joint Tarsometatarsal and Intermetatarsal Joints Metatarsophalangeal and interphalangeal Joints Plantar Arches Muscles of the Foot Extrinsic muscles cross ankle Intrinsic muscles have both attachments within the foot. Toe Flexion and Extension Inversion and Eversion Pronation and Supination Loads on the Foot Structures of foot anatomically linked to evenly distribute load over whole foot. 50% of BW distributed through subtalar joint to calcaneous − Remaining 50% transmitted across metatarsal heads. Architecture of food affects loading − Flat arch: reduced forefoot load − High arch: increased forefoot load Summery Lower extremity well adapted to function of weight bearing and locomotion The hip is a typical ball and socket joint The knee is a large, complex joint composed of two side-by-side condyloid articulations The ankle includes articulations of the tibia and fibula with the talus. Like the hand, the foot is composed of many small bone their articulations Don’t Forget ! Muscles of the Hip. (p.p. 231). Sample Problem 8.1 (p.p. 237). Muscles of the Knee. (p.p. 242). Sample Problem 8.2 (p.p. 246). Muscles of the Ankle and Foot. (p.p. 256). Any other useful book! Thank you for Listening.