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).
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