Chapter 8: The Biomechanics of the Upper Extremities

1. 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

2. 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.

3. 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.

4. Movements at the Hip • Pelvic Girdle • Flexion • Extension • Abduction • Adduction • Medial and Lateral Rotation of Femur • Horizontal Abduction and Adduction

5. 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.

6. 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

7. 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

8. Movements at the Knee • Flexion and Extension • Popliteus • Quadriceps • Rotation and Passive Abduction and Adduction • Patellofemoral Joint Motion

9. 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

10. 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

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

12. Structure of the Foot • Subtalar Joint • Tarsometatarsal and Intermetatarsal Joints • Metatarsophalangeal and interphalangeal Joints • Plantar Arches

13. 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

14. 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

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

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

17. 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