Exercise Science 5
Musculoskeletal System: Lower Extremity
Chapter 3
Nicole Mendola, MS, RCEP, C-EP, GEI, EIM III
Objectives
- Discuss bone, joints and muscles of the lower body including:
- Hip/pelvis
- Knee
- Foot/ankle
- Identify the origin and insertion of muscles.
- Identify the direction of pull and joint actions of muscles.
Pelvis and Hip
Bones
- Sacrum
- Innominate (os coxae) consists of:
- Fused ilium (largest pelvic bone)
- Ischium
- Pubis on each side (usually fuse by puberty)
- The two sides of the pelvis join:
- Anteriorly at pubic symphysis
- Posteriorly at sacroiliac joints
Structure of Pelvis
- Anterior Superior Iliac Spine (ASIS) of ilium is a bony protuberance serving as a muscle attachment site.
- The sacrum articulates with the pelvis on each side, forming sacroiliac joints.
- The sacrum also articulates with each femur at the acetabulum, forming hip joints.
Ligaments
- Sacroiliac Joint Ligaments:
- Anterior ligament
- Posterior ligament
- Interosseous ligament
- Hip Joint Ligaments:
- Iliofemoral ligament
- Pubofemoral ligament
- Ischiofemoral ligament
- These ligaments stabilize the hip joint by forming a strong, dense joint capsule.
Joints
- Pubis Symphysis connects each side of pelvic girdle anteriorly (amphiarthrodial joint).
- Sacroiliac Joint connects sacrum to ilium on each side (gliding joint).
- Hip Joint:
- One of the most mobile joints
- Type: ball and socket joint
- Articulates proximal femur with acetabulum of pelvis.
Movements of Pelvis and Hip
- Pelvic Girdle Movements (3 planes):
- Rotation (transverse plane)
- Lateral tilt (frontal plane)
- Anterior and posterior tilt (sagittal plane)
- Hip Joint Movements (3 planes):
- Flexion/Extension (sagittal plane)
- Abduction/Adduction (frontal plane)
- Internal/External Rotation (transverse plane)
- Circumduction (combined plane movements)
Muscles Acting on Pelvis and Hip
Anterior Muscles
Iliopsoas:
- Iliacus
- Psoas Major
- Psoas Minor
- Origin: ?
- Insertion: ?
- Action: Flexion of hip.
Pectineus:
- Origin: ?
- Insertion: ?
- Action: Flexion, adduction, internal rotation of hip.
Rectus Femoris (part of Quadriceps):
- Origin: ?
- Insertion: ?
- Action: Flexion of hip.
Sartorius:
- Origin: ?
- Insertion: ?
- Action: Flexion, abduction, external rotation of hip.
Tensor Fasciae Latae:
- Origin: ?
- Insertion: ?
- Action: Abduction, flexion of hip.
Medial Muscles
Gracilis:
- Origin: ?
- Insertion: ?
- Action: Adduction of hip.
Adductors:
- Longus
- Brevis
- Magnus
- Origin: ?
- Insertion: ?
- Action: Adduction of hip.
Posterior Muscles
Gluteus Maximus:
- Origin: ?
- Insertion: ?
- Action: Extension, lateral rotation, abduction of hip.
Gluteus Medius:
- Origin: ?
- Insertion: ?
- Action: Abduction, medial rotation of hip.
Gluteus Minimus:
- Origin: ?
- Insertion: ?
- Action: Abduction, medial rotation of hip.
6 Deep Lateral Rotators:
- Piriformis
- Superior gemellus
- Internal obturator
- Inferior gemellus
- Quadratus femoris
- External obturator
Hamstrings:
- Biceps Femoris:
- Origin: ?
- Insertion: ?
- Action: Extension, lateral rotation of hip.
- Semimembranosus / Semitendinosus:
- Origin: ?
- Insertion: ?
- Action: Extension, internal rotation of hip.
Knee
Bones
- Knee Joint:
- Consists of:
- Distal Femur
- Proximal Tibia (major weight-bearing bone of leg)
- Patella (kneecap):
- Triangular sesamoid bone, located within the patellar tendon of quads, protects anterior knee, creates improved angle of pull for quads.
Ligaments
- Major Ligaments:
- Cruciate Ligaments:
- Anterior cruciate ligament (ACL)
- Posterior cruciate ligament (PCL)
- Collateral Ligaments:
- Medial collateral ligament with tibia
- Lateral collateral ligament with fibula
- Aid in stability of knee.
Joints
- Knee is the largest joint in the body.
- Tibiofemoral Joint (primary joint of knee): Hinge joint.
- Patellofemoral Joint: Arthrodial joint formed by posterior aspect of patella and patellofemoral groove between condyles of femur.
Menisci
- Fibrocartilage discs (menisci) attached to tibial plateaus and knee joint capsule.
- Functions:
- Improve congruency of joint surfaces.
- Add stability.
- Aid in shock absorption.
- Provide joint lubrication.
- Aid in load-bearing.
- Add anterior/posterior stability.
- Protect articular cartilage.
Movements
- Knee's Normal ROM: 140° in the sagittal plane.
- 0° represents full extension.
- 140° represents full flexion.
- When flexed:
- Tibiofemoral joint capable of 30° internal and 45° external rotation (transverse plane).
Quadriceps Muscles
Anterior Muscles
Rectus Femoris:
- Origin: ?
- Insertion: ?
- Action: Extension of knee.
Vastus Lateralis:
- Origin: ?
- Insertion: ?
- Action: Extension of knee.
Vastus Medialis:
- Origin: ?
- Insertion: ?
- Action: Extension of knee.
Vastus Intermedius:
- Origin: ?
- Insertion: ?
- Action: Extension of knee.
Posterior Muscles
Hamstrings:
- Biceps Femoris:
- Origin: ?
- Insertion: ?
- Action: Flexion, external rotation of knee.
- Semitendinosus / Semimembranosus:
- Origin: ?
- Insertion: ?
- Action: Flexion, internal rotation of knee.
Sartorius:
- Origin: ?
- Insertion: ?
- Action: Flexion at knee.
Gracilis:
- Origin: ?
- Insertion: ?
- Action: Flexion of knee.
Popliteus:
- Origin: ?
- Insertion: ?
- Action: Flexion of knee, unlocks extended knee by rotating femur on tibia.
Gastrocnemius:
- Origin: ?
- Insertion: ?
- Action: Flexion of knee.
Ankle and Foot
Bones
- Foot has 26 articulating bones categorized into 3 functional units:
- Anterior - Forefoot:
- 5 metatarsals
- 14 phalanges
- Middle - Midfoot:
- 5 tarsal bones (Navicular, Cuboid, 3 Cuneiforms)
- Posterior - Hindfoot:
- Talus and Calcaneus.
- The ankle is formed by the fibrous union of distal tibia, medial malleolus of tibia and lateral malleolus of fibula.
Ligaments
- Approximately 100 ligaments in ankle and foot region.
- Lateral side of ankle ligaments:
- Anterior talofibular ligament
- Posterior talofibular ligament
- Calcaneofibular ligament
- Medial side of ankle ligaments (Deltoid ligament complex):
- Tibiocalcaneal ligament
- Anterior tibiotalar ligament
- Posterior tibiotalar ligament
- Tibionavicular ligament
- Plantar calcaneonavicular (spring ligament): helps support talus, maintains longitudinal arch.
Joints
- Ankle Joint: Synovial, hinge-type joint between distal tibia/fibula and dome of talus.
- Subtalur Joint: Synovial joint between talus and calcaneus.
- Additional joints include:
- Tarsometatarsal
- Intermetatarsal
- Metatarsophalangeal
- Interphalangeal.
Movements
- Ankle Movements:
- 15-20° dorsiflexion (sagittal plane)
- 50° plantar flexion (sagittal plane)
- 20-30° inversion (frontal plane)
- 5-15° eversion (frontal plane).
Muscles Acting on Ankle and Foot
Anterior Muscles
Tibialis Anterior:
- Origin: ?
- Insertion: ?
- Action: Dorsiflexes ankle, inverts foot.
Peroneus Tertius:
- Origin: ?
- Insertion: ?
- Action: Dorsiflexes ankle, everts foot.
Extensor Digitorum Longus:
- Origin: ?
- Insertion: ?
- Action: Dorsiflexes ankle, extends digits 2-5.
Extensor Hallucis Longus:
- Origin: ?
- Insertion: ?
- Action: Dorsiflexes ankle, extends toe.
Lateral Muscles
- Peroneus Longus and Brevis:
- Origin: ?
- Insertion: ?
- Action: Plantar flexes ankle, everts foot.
Posterior Muscles
Gastrocnemius:
- Origin: ?
- Insertion: ?
- Action: Plantar flexes ankle.
Soleus:
- Origin: ?
- Insertion: ?
- Action: Plantar flexes ankle.
Deep Posterior Muscles:
- Tibialis Posterior:
- Origin: ?
- Insertion: ?
- Action: Plantar flexes ankle, inverts foot.
- Popliteus:
- Origin: ?
- Insertion: ?
- Action: Plantar flexes ankle, inverts foot.
- Flexor Digitorum Longus:
- Origin: ?
- Insertion: ?
- Action: Plantar flexes ankle, inverts foot.
- Flexor Hallucis Longus:
- Origin: ?
- Insertion: ?
- Action: Plantar flexes ankle, inverts foot.