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