Chapter 8: The Biomechanics of the Upper Extremities Basic Biomechanics, 4th edition Susan J. Hall Presentation Created by TK Koesterer, Ph.D., ATC Humboldt 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. Describe the biomechanical contributions to common injuries of the lower extremity.

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.

Common Injuries of the Hip Fractures Usually of femoral neck, a serious injury usually occurring in elderly with osteoporosis Contusions Usually in anterior aspect of thigh, during contact sports Strains Usually to hamstring during sprinting or overstriding

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 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

Common Injuries of the Knee and Lower Leg ACL injuries PCL injuries MCL injuries Prophylactic Knee Bracing Meniscus Injuries Iliotibial Band Friction Syndrome Breaststroker’s Knee Patellofemoral Pain Syndrome Shin Splints

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

Common Injuries of the Ankle and Foot Ankle Sprains Inversion sprain much more common than eversion sprains Overuse Injuries Tendonitis Excessive pronation Stress Fractures

Common Injuries of the Ankle and Foot Alignment Anomalies of Foot: Varus Valgus Injuries Related to High and Low Arch Structures

Summary 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