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

Anterior reinforcement from iliofemoral and

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 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

A large synovial with three articulations within . Tibiofemoral Joint Menisci : 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

Movements of the ankle: −Dorsiflexion: −Tibialis anterior −Extensor digitorum longus −Peroneus tertius −Plantar Flexion: −Two heads of gastrocnemius −Soleus Structure of the

Subtalar Joint

Tarsometatarsal and Intermetatarsal

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 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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