Muscles and Movements of Lower Extremity – Ch 8 Objectives

1. Muscles and Movements of Lower Extremity – Ch 8 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.

2. Lower Extremity Outline • Hip Joint • Structure , Loads, and Muscles and Movements • Knee Joint • Structure, Loads, Muscles and Movements • Common knee injuries – patellar chondromalacia (a.k.a. runners knee) and anterior cruciate tear • Ankle Joint • Structure, Muscles and Movements • Common ankle and foot injuries - plantar fascitis, pronated feet • Misalignment problems of lower extremity • Websites • Homework

3. Hip joint structure: Front View

4. Loads on the Hip • During swing phase of walking: • Compression forces on hip greater than body weight (due to muscle tension) 250% body weight (BW) • Increases with hard-soled shoes • Increases with gait increases (both support and swing phase) (500% BW when running 3.5 m/s) • Body weight, impact forces translated upward thru skeleton from feet and muscle tension contribute to compressive load on hip.

5. Compressive forces on hip jt Socket while walking may exceed 3 to 4 times body wt, 5-6 times bw while jogging, and 8-9 times bw while stumbling Use law of cosines:

6. Hip Joint Muscles • Uni-articular muscles • Flexion - iliopsoas • Extension - gluteus maximus • Abduction - gluteus medius and minimus • Adduction - adductor brevis, longus, & magnus • Biarticular muscles • Hip flexion, knee flexion - sartorius • Hip flexion,knee extension - rectus femoris • Hip extension, knee flexion - hamstrings • Note passive and active insufficiency of biarticular muscles

7. Muscles of Lower Extremity:

8. Hip Jt Muscle Vectors:

9. Thigh muscles in cross-section:

10. Physiological cross-sectional area (PCSA) of hip jt muscles Why are lateral rotators & gluteii muscles so large?

11. 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

12. Knee Joint • Ligaments and cartilage • medial and lateral collateral ligaments • anterior and posterior cruciate ligaments • medial and lateral meniscus • Muscles and movements • Extensors • quadriceps femoris (rectus femoris, vastus lateralis, vastus medialis, vastus intermedius) • Flexors • hamstrings (semitendinosus, semimembranosus, biceps femoris)

13. Knee Joint Structure: 25% of Alpine skiing injuries are ligament injuries Peripatellar pain (runner’s knee) caused by imbalance of stress on patella

14. Lower Extremity Misalignment: Q angle is larger in females due to Wider hip structure, increasing potential for PFPS (Patellofemoral pain syndrome)

15. Quadriceps Tendon and Patella Force Lines Compressive force at PFJ is ½ body wt during normal walking, and over 3 times bw during stair climbing Comp force increases as knee flexion Angle increases

16. Cruciate Ligaments and Shear Stress

17. Loads on Knee • Forces at tibiofemoral Joint • Shear stress is greater during open kinetic chain exercises such as knee extensions and knee flexions • Compressive stress is greater during closed kinetic chain exercises such as squats and weight bearing exercises. • 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

18. Thigh muscles in cross-section:

19. PCSA of Muscles Crossing Knee

20. Common Injuries of the Knee and Lower Leg • Patellofemoral Pain Syndrome • Shin Splints • Anterior cruciate ligament (ACL) injuries • Posterior cruciate ligament (PCL) injuries • Medial collateral ligament (MCL) injuries • Meniscus Injuries • Iliotibial Band Friction Syndrome • Breaststroker’s Knee

21. Foot and Ankle joint structure • Bones and arches of foot • Tibia, fibula, calcaneus, talus, other tarsals, metatarsals, phalanges • Longitudinal arch, transverse arch • plantar fascia • Movements of ankle - talocrural joint • Movements of foot - subtalar, intertarsal, intermetatarsal, interphalangeal

22. Bones of Shank and Foot:

23. Ankle Joint Muscles and Movements • Anterior compartment - All dorsiflex • Tibialis anterior (also inverts) • Extensor digitorum longus (also everts) • Posterior compartment - All plantar flex • Tibialis posterior (also inverts), gastrocnemius (also flexes knee), & soleus • Lateral compartment - All plantar flex & evert • Peroneus longus & brevis • Foot pronation and supination

24. Ankle and Foot Muscles:

25. Percent PCSA of Muscles Crossing Ankle

26. Subtalar Axis:

27. Foot Pronation and Tibial Torsion:

28. Rearfoot Movement During Running:

29. Plantar Fascium • What is the plantar fascium? - attaches to calcaneus posteriorly and to the first row of phalanges anteriorly • What is its function? • passive intertarsal stabilization

30. Arches of the Foot:

31. Plantar Fascium:Plantar fascitis is 4th most common cause of pain among runners(1st – knee pain, 2nd – shin splints, 3rd- achilles tendonitis)

32. Plantar Fascitis – 4th leading cause of pain in runners • What causes plantar fascitis(inflamation of plantar fascium)? • anatomic anomalies • microtears in fascium and bone spurs • inadequate flexibility of plantar flexors • inadequate strength of plantar flexors • functional pronation (eversion and abduction) • overuse • overweight • poorly designed and poorly fitted shoes • running and jumping on hard surfaces • sudden increase in stress • Treatment • remove the cause(s) • Therapeutic treatment to promote body’s natural healing • NSAIDS • Intermittent ice and heat • Ultrasound, diathermy, massage

33. Patellar Chrondomalacia (a.k.a. Runner’s Knee) – leading cause of pain in runners) • Primary cause is imbalance in forces on patella • Increased Q angle • Pronated feet • Tissues affected • Degrading of articular cartilage of patella & femoral condyles • Fluid collection, causing joint stiffness • Symptoms • Pain around patella with no particular injury causing it • Worse going upstairs and downstairs, or after sitting awhile • Feels like knee needs to be stretched • Prevention/treatment • Surgery is seldom beneficial • Wet test – walk with wet feet on floor and determine if you have a hypermobile foot. If so, purchase shoes and/or orthotics to decrease degree of foot pronation • Exercises to increase strength/endurance of vastus medialis

34. Runner’s knee, cont’d Wet test: Safe exercise to develop vasti muscles Do not use knee sleeves! Do not bend knee more than 20-30 degrees while doing extensions with resistance!

35. Websites for Muscles, Movements, & Problems of Lower Extremity • Steadman-Hawkins Sports Medicine Clinic • Shoulder joint impingement syndrome • Carpal tunnel syndrome • Patellofemoral pain syndrome • Lumbar disc herniation Homework on lower extremity: (Due Wed, Oct 20) Introductory problems, p 263: 9,10 Additional problems, p 263-264: 6