Lecture Notes: Lower Extremity Bones and Muscles PDF

Principles of Human Anatomy ANAT 3651 Lecture notes: Bones and Muscles of the Lower Extremity Objectives: 1. Identify bones that form the pelvic girdle and their features 2. Identify bones of the lower limb and their features 3. Describe the anatomy of the hip & knee joints 4. Identify muscles of th...

Principles of Human Anatomy ANAT 3651 Lecture notes: Bones and Muscles of the Lower Extremity Objectives: 1. Identify bones that form the pelvic girdle and their features 2. Identify bones of the lower limb and their features 3. Describe the anatomy of the hip & knee joints 4. Identify muscles of the lower extremity with their origins, insertions, & movements ______________________________________________________________________ Bones of the Lower Extremity Below are the bones and bony features of the lower extremity that you should be familiar with. Pelvic girdle The pelvic girdle is formed by the irregularly-shaped os coxae (or hip bones) on the left and right side. The os coxae is formed by the fusion of three bones: ilium, ischium, and pubis. The entirety of the pelvis is formed by the left and right os coxae, sacrum, and coccyx. Similar to the pectoral girdle, the os coxae is the connection of the lower limb to the axial skeleton. Os coxae o Ilium- superior part of os coxae o Ischium- posterior part of os coxae o Pubis- anterior part of os coxae o Iliac crest- ridge of bone on the top of the ilium o Anterior superior iliac spine (ASIS)- projection at the anterior end of the iliac crest o Anterior inferior iliac spine- projection of bone just below the ASIS o Acetabulum- depression formed by the ilium, ischium, and pubis; forms part of the hip joint o Superior pubic ramus o Ischiopubic ramus- strip of bone connecting the ischium and pubis o Pubic tubercle- small bump of bone at the medial end of the superior pubic ramus o Obturator foramen- large foramen between the ischium and pubis o Ischial tuberosity- large, rough bump of bone on the ischium o Lesser sciatic notch- small notch above the ischial tuberosity o Ischial spine- projection of bone between the greater and lesser sciatic notches Lower Extremity 1 o Greater sciatic notch- large notch between the ischial spine and iliac crest o Iliac fossa- large depression on the medial side of the ilium o Pubic symphysis- cartilaginous joint between the left and right pubic bones Lower limb bones Femur- bone of the thigh o Head- articulates with the acetabulum of the os coxae to form the hip joint o Greater trochanter- projection on the proximal, lateral side of the femur o Lesser tubercle- projection on the proximal, medial side of the femur o Linea aspera- ridge of bone along posterior side of the shaft o Adductor tubercle- Small bump above the medial epicondyle o Medial condyle- medial articular surface at the distal end of the femur, articulates with the tibia o Lateral condyle- lateral articular surface at the distal end of the femur, articulates with the tibia o Medial epicondyle- projection of bone above the medial condyle o Lateral epicondyle- projection of bone above the lateral condyle Patella- largest sesamoid bone in the body, grows within the quadriceps tendon, only articulates with the femur Fibula- lateral bone of the leg o Head- articulates with the lateral side of the proximal tibia o Lateral malleolus- projection of bone at the distal end Tibia- medial bone of the leg o Tibial tuberosity- anterior projection of bone at the proximal end o Medial malleolus- projection of bone at the distal end Interosseous membrane- dense connective tissue connecting the shafts of the tibia and fibula Tarsals- set of seven bones of the proximal foot o Talus o Calcaneus o Navicular o Cuboid o Cuneiforms (3) Metatarsals- five long bones in the foot Lower Extremity 2 Phalanges- toe bones, each toe has three phalanges (proximal, intermediate, and distal) except the big toe (hallux) only has two (proximal and distal) The feet have a three arch system: two longitudinal (medial and lateral) and one transverse. The foot is a stiff structure and the arches act like springs during walking. These arches are an adaptation to bipedal locomotion. Joints of the Lower Extremity Hip joint o Between the acetabulum of the os coxae and head of the femur o Ball and socket joint, multiaxial o Supported by ligaments and many muscles o Ligaments of hip joint ▪ Iliofemoral ligament ▪ Ischiofemoral ligament ▪ Pubofemoral ligament o Movements at this joint: ▪ Medial rotation-lateral rotation ▪ Abduction-adduction ▪ Flexion-extension Knee joint o Between the distal femur and proximal tibia o Hinge joint, uniaxial o Largest synovial joint of the body o Internal ligaments: ▪ Anterior cruciate ligament ▪ Posterior cruciate ligament o External ligaments: ▪ Medial collateral ligament ▪ Lateral collateral ligament o Cartilage: ▪ Medial meniscus ▪ Lateral meniscus o Movements at this joint: ▪ Flexion-extension o Clinical correlate: Unhappy triad ▪ Blow to the lateral knee when foot is planted can result in torn medial meniscus, ACL, and medial collateral ligament Ankle joint o Between the distal tibia and fibula and the talus, has two articulations (proximal and distal) Lower Extremity 3 o Condylar joint, biaxial o Movements at this joint: ▪ Flexion (plantar flexion)-extension (dorsiflexion) ▪ Inversion-eversion Metatarsophalangeal joints o Between metatarsals and phalanges o Condylar joints, biaxial o Movements at these joints: ▪ Flexion-extension ▪ Abduction-adduction Interphalangeal joints o Between phalanges o Two joints in digits 2-5, only one in hallux o Hinge joints, uniaxial o Movements at these joints: ▪ Flexion-extension Muscles of the Lower Extremity Muscles that move the thigh The muscles that move the thigh can be divided into groups or compartments: from the abdomen (psoas major and iliacus), gluteal region (gluteus maximus, medius, minimus, and piriformis), and medial compartment (gracilis, adductor magnus, longus, and brevis). Psoas major and iliacus originate from within the abdomen and have a common tendon (iliopsoas tendon) that inserts onto the lesser tubercle. Gluteus medius and minimus are deep to gluteus maximus and are important hip abductors that allow us to pull our body weight over our foot when walking. This is another adaptation to bipedal locomotion. In the medial thigh, the adductor muscles are layers superficial to deep: adductor longus, adductor brevis, and adductor magnus. You can think of this as a “brevis sandwich” with adductor brevis in the middle. Muscle Psoas major Iliacus Gluteus maximus Origin Lumbar vertebrae Iliac fossa of ilium Iliac crest, sacrum Gluteus medius Gluteus minimus ilium ilium Insertion Lesser trochanter of femur Lesser trochanter of femur Iliotibial tract and linea aspera Greater trochanter Greater trochanter Action Flex thigh Flex thigh Extend thigh Abduct thigh Abduct thigh Lower Extremity 4 Piriformis Gracilis Adductor magnus Sacrum pubis Pubis & ischium Adductor longus Adductor brevis Pubis & ischium Pubis & ischium Greater trochanter of femur Laterally rotates thigh Medial, proximal tibia Adduct thigh Adductor tubercle of femur, Adduct thigh linea aspera Linea aspera Adduct thigh Linea aspera Adduct thigh Muscles that move the thigh and leg The muscles of the anterior (quadriceps, sartorius, and tensor fasciae latae) and posterior (hamstrings) compartments of the thigh have muscles that generally produce movements at both the hip and knee joints. The quadriceps muscle is a muscle that has four heads: rectus femoris, vastus lateralis, vastus intermedius, and vastus medialis. These muscles come together as the quadriceps tendon which contains the patella. The muscles insert into the tibial tuberosity via the patellar ligament. Tensor fasciae latae is a muscle found in the anterior, lateral thigh, but technically part of the gluteal region based on innervation and blood supply. The muscle originates from the ASIS but connects to the iliotibial tract (or IT tract/band) before inserting into the proximal tibia. The iliotibial tract is a thickening of the deep fascia (fascia lata) that surrounds the thigh. The muscles in the posterior compartment are the semitendinosus, semimembranosus, and biceps femoris. Biceps femoris has two heads: a long head and short head. Semitendinosus, semimembranosus, and the long head of biceps femoris are considered hamstring muscles because they originate from the ischial tuberosity and insert on the tibia, crossing both the hip and knee joints. The short head of biceps femoris is not considered a hamstring muscle since it only crosses the knee joint. The sartorius, gracilis, and semitendinosus muscles all have a common insertion on the medial tibia via a tendinous structure called the pes anserinus or “ducks foot”. To remember these muscles, remember the saying “Say Grace before Tea” for Sartorius, Gracilis, and semiTendinosus. Muscle Sartorius Tensor fasciae latae Rectus femoris Vastus lateralis Origin Anterior superior iliac spine Iliac crest Insertion Medial tibia (via pes anserinus) Iliotibial band/tract Action Flexes & laterally rotates thigh, flexes leg Abduct thigh, stabilize hip & knee Anterior inferior iliac Tibial tuberosity via patellar Flex thigh, extend leg spine ligament Linea aspera Tibial tuberosity via patellar Extend leg ligament Lower Extremity 5 Vastus intermedius Linea aspera Vastus medialis Linea aspera Semimembranosus Ischial tuberosity Semitendinosus Ischial tuberosity Biceps femoris Long head: ischial tuberosity Short head: linea aspera Tibial tuberosity via patellar Extend leg ligament Tibial tuberosity via patellar Extend leg ligament Proximal, medial tibia Extend thigh, flex leg Proximal, medial tibia (via Extend thigh, flex leg pes anserinus) Head of fibula Extend thigh (not short head), flex leg Muscles that move the foot The muscles that move the foot at the ankle are found in the leg but send their tendons to insert on the foot or toes and can be divided into anterior, lateral, and posterior compartments. The anterior (extensor) compartment muscles include tibialis anterior, extensor hallucis longus, and extensor digitorum longus. Extensor digitorum longus can be identified by the tendons traveling to digits 2-5 and extensor hallucis longus can be identified by the tendon traveling to the distal phalanx of the hallux (big toe). The lateral compartment muscles include fibularis longus and brevis. The tendons from these muscles wrap around the lateral malleolus (of the fibula) before inserting on the foot. The tendon of fibularis longus travels across the plantar side (bottom) of the foot to insert all the way on the first metatarsal (of the big toe)! The posterior (flexor) compartment can be divided into superficial and deep groups. The superficial group includes gastrocnemius and soleus which join together to form the calcaneal (Achilles) tendon that inserts on the calcaneus. Gastrocnemius is a twoheaded muscle that can be observed on the posterior leg. Soleus is a flat muscle just deep to gastrocnemius. The deep group has similar muscles to the anterior compartment, just on the posterior side: tibialis posterior, flexor hallucis longus, and flexor digitorum longus. They can be distinguished in similar ways to the muscles of the anterior compartment. The tibialis anterior and tibialis posterior muscles act together to invert the foot from both anterior and posterior compartments. Muscle Tibialis anterior Origin Insertion Action Proximal tibia 1st metatarsal Extend (dorsiflex) foot; invert foot Lower Extremity 6 Extensor digitorum longus Extensor hallucis longus Tibia and fibula Fibula Distal phalanges of digits 2-5 Distal phalanx of hallux Fibularis longus Fibula 1st metatarsal-plantar side Evert foot Fibularis brevis Fibula 5th metatarsal Evert foot Gastrocnemius Femoral condyles Flex (plantarflex) foot Soleus Proximal tibia and fibula Tibia and fibula Calcaneus via calcaneal tendon Calcaneus via calcaneal tendon 1st metatarsal Tibialis posterior Flexor digitorum longus Tibia Flexor hallucis longus Fibula Distal phalanges of digits 2-5 Distal phalanx of hallux Extend toes 2-5; Extend (dorsiflex) foot Extend hallux, Extend (dorsiflex) foot Flex (plantarflex) foot Flex (plantarflex) foot, invert foot Flex toes 2-5; flex (plantarflex) foot Flex hallux, flex (plantarflex) foot Lower Extremity 7