Lower Extremity: Lesson 5 Study Notes

Lower Extremity: Lesson 5 Study Notes

Anatomy Review

  • Topics covered include the Foot, Ankle, Tibia/Fibula, and Knee.

Foot Anatomy

  • General Characteristics:

    • Significant variation in thickness observed transitioning from toes to heel.

    • Composed of 26 bones organized into three main parts:

    • Tarsus (Tarsal Bones): The bones constituting the ankle.

    • Metatarsals: The bones forming the instep or arch of the foot.

    • Phalanges: The bones of the toes.

Divisions of the Foot

  • The foot is often segmented into:

    • Forefoot: Includes metatarsals and phalanges.

    • Midfoot: Comprises 5 out of the 7 tarsal bones.

    • Hindfoot: Contains the remaining 2 tarsal bones.

Phalanges

  • Number of Bones:

    • Total of 14 phalanges.

    • Great Toe: Contains 2 phalanges.

    • Other Toes: Each of the remaining four toes comprises 3 phalanges.

  • Structure:

    • Each phalanx consists of a base, body, and head (except for the great toe).

    • Naming by location: Distal, middle, and proximal.

  • Interphalangeal (IP) Joints:

    • Named based on their locations, classified as synovial, diarthrodial hinge joints.

Metatarsals

  • Count and Structure:

    • There are 5 metatarsals: Numbered from 1 to 5, starting from the medial aspect (great toe side).

    • Each metatarsal consists of a body (shaft) and two articular extremities.

    • Proximal End: Known as the base.

    • Distal End: Known as the head (the five heads form the ball of the foot).

  • Articulations:

    • Distal ends (heads) connect to the bases of proximal phalanges at Metatarsophalangeal (MTP) joints.

Tarsals

  • Total Count: Comprises 7 tarsal bones of the ankle:

    • Calcaneus (Os Calcis): The bone of the heel.

    • Talus: Superiormost position of the foot, articulates with the tibia and fibula.

    • Navicular: Located between the calcaneus and the three cuneiforms.

    • Cuboid: Situated on the lateral side between the calcaneus and fourth and fifth metatarsals.

    • Cuneiforms: Three bones differentiated as medial, intermediate, and lateral.

Calcaneus

  • The largest and strongest tarsal bone:

    • Position: Projects posteriorly and medially.

    • Features:

    • Tuberosity: Posterior-inferior section providing attachment to the Achilles tendon.

    • Contains 3 articular facets: Anterior, middle, and posterior for articulation with the talus.

    • Calcaneal Sulcus: A groove on the superior surface between the middle and posterior facets, paired with a similar groove on the talus, forming the sinus tarsi.

Talus

  • Second largest tarsal bone, occupying the superior position:

    • Articulations: Connects with the tibia, fibula, calcaneus, and navicular bone.

    • Forming the subtalar joint with the calcaneus.

    • Contains a groove (sulcus tali) which assists in forming the sinus tarsi.

    • The trochlear surface on the superior side articulates with the tibia; anteriorly directed head joins with the navicular bone.

Cuneiforms

  • Naming and Location:

    • Medial, Intermediate, and Lateral cuneiforms, positioned centrally between the navicular and the 1st, 2nd, and 3rd metatarsals.

    • Size: Medial cuneiform is the largest, while the Intermediate is the smallest.

Sesamoid Bones

  • Definition: Small, detached bones located within tendons, often found under stress areas near joints.

  • Usually located on the plantar surface beneath the head of the first metatarsal, susceptible to fractures which can be notably painful.

Foot Articulations

  • Interphalangeal Articulations (IP): Between phalanges; classified as synovial hinge joints.

    • PIP: Proximal interphalangeal joints.

    • DIP: Distal interphalangeal joints.

    • Metatarsophalangeal Articulations (MTP): Between bases of proximal phalanges and heads of metatarsals.

Joints of the Foot

  • Key Joints:

    • Distal interphalangeal joints, proximal interphalangeal joints, and metatarsophalangeal joints, as well as articulations among metatarsal and tarsal bones, notably including:

    • Tarsometatarsal Articulations (TMT): Synovial gliding joint connecting bases of metatarsals to tarsals.

    • Intertarsal Articulations: Joints between tarsals.

Ankle Joint

  • Formed by the articulation of the talus with:

    • Lateral malleolus of fibula.

    • Inferior surface of tibia.

    • Medial malleolus of tibia.

  • Classified as a synovial hinge-type joint allowing for flexion (dorsiflexion) and extension (plantar flexion).

Lower Leg Anatomy

  • Bones: Consists of the Tibia and Fibula.

    • Tibia: Second largest bone in the body, located on the medial side, primarily weight-bearing.

    • Fibula: Positioned laterally and slightly posterior; serves a non-weight-bearing role.

Tibia

  • Classification: Long bone with a body and two expanded extremities:

    • Proximal End: Features two prominent processes (medial and lateral condyles) forming smooth articular facets called tibial plateaus for knee joint articulation with the femur.

Proximal Tibia Structure

  • Intercondylar Eminence: Sharp projection positioned between the two tibial plateaus.

    • Ends in two peak-like processes known as medial and lateral intercondylar tubercles.

Tibiofibular Joint

  • Located at the lateral condyle of the tibia; features an articulating facet that connects with the head of the fibula, termed as the proximal tibiofibular joint; classified as a synovial gliding joint.

Distal Tibia Characteristics

  • Medial Malleolus: Palpable landmark, critical in forming the ankle mortise.

  • Fibular Notch: Triangular depression on the distal tibia’s lateral aspect for fibular articulation.

    • The distal tibiofibular joint is described as amphiarthrotic (slightly movable) and is classified as a fibrous syndesmosis joint.

    • The underside facilitates articulation with the talus for proper ankle mortise functioning.

Fibula Overview

  • Classified as a long, slender bone:

    • Head: The proximal end, articulating with the tibia at the proximal tibiofibular joint.

    • Lateral Malleolus: The distal end which forms part of the ankle mortise, positioned lower than the medial malleolus.

Knee Anatomy

  • Formed by combining femoral condyles with tibial plateaus.

    • Condyles: Medial and lateral femoral condyles at the distal femur; medial condyle is larger.

    • Classified as a synovial hinge-type joint.

    • Protected by the Patella: A sesamoid bone located on the anterior surface of the femur, which consists of a flat, triangular structure.

Knee Joint Complexity

  • Considered one of the most intricate joints in the human body due to the involvement of the femur, tibia, and patella connected by essential ligaments:

    • Anterior Cruciate Ligament (ACL)

    • Posterior Cruciate Ligament (PCL)

    • Tibial Collateral Ligament (TCL)

    • Fibular Collateral Ligament (FCL)

Stabilization and Protection

  • Stabilized and cushioned by menisci: fibrocartilage disks, which provide both stability and shock absorption.

    • Specifically includes medial and lateral menisci often subject to tears.

Patella Details

  • Recognized as the largest, most consistent sesamoid bone:

    • Location: Positioned on the distal, anterior surface of the femur.

    • Develops within the quadriceps femoris tendon between ages 3-5.

    • Shape: Flat, triangular; apex points towards the knee, situated about ½ inch above the knee joint space, while the base is regarded as the superior border.

Conclusion and Homework

  • Students are encouraged to keep up with the readings and homework outlined in the syllabus.