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.

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

Hip joint structure:

Front View

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.

Compressive forces on hip jtSocket 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:

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

Muscles of Lower

Extremity:

Hip Jt Muscle Vectors:

Thigh muscles

in cross-

section:

Physiological cross-

sectional area (PCSA) of

hip jt musclesWhy are lateral rotators& gluteii muscles so large?

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

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)

Knee Joint Structure:

25% of Alpine skiing injuries are ligament injuries Peripatellar pain (runner’s knee) caused by imbalance of stress on patella

Lower Extremity Misalignment:

Q angle is larger in females due to Wider hip structure, increasing potential for PFPS (Patellofemoral pain syndrome)

Quadriceps Tendon and Patella Force LinesCompressive force at PFJ is ½ bodywt during normal walking, and over 3 times bw during stair climbingComp force increases as knee flexionAngle increases

Cruciate Ligaments and Shear Stress

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

Thigh muscles

in cross-

section:

PCSA of Muscles Crossing Knee

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

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

Bones of Shank and Foot:

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

Ankle and Foot Muscles:

Percent PCSA of Muscles Crossing Ankle

Subtalar Axis:

Foot Pronation and Tibial Torsion:

Rearfoot Movement During Running:

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

Arches of the Foot:

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

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

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

Runner’s knee, cont’d

Wet test:

Safe exercise to develop vasti musclesDo not use knee sleeves!Do not bend knee more than 20-30 degrees while doing extensions with resistance!

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: 9,10Additional problems, p 263-264: 6