LL anatomy Spring 2022 part3 2

Lower Limb Anatomy

Overview

  • Instructor: Dr. Muna Nasser Kadhom

  • Institution: University of Sharjah

  • Contact: mkadhom@sharjah.ac.ae

The Tibia

  • Main bone of the leg, commonly referred to as the shin.

  • Functions as a weight-bearing structure, making it the second largest bone in the body.

  • Articulations:

    • Proximal end: articulates at the knee.

    • Distal end: articulates at the ankle joint.

Structural Details of the Tibia

Proximal End

  • Features: Medial and lateral condyles that provide a flat surface called the tibial plateau for articulation with femoral condyles (knee joint).

  • Intercondylar Eminence:

    • Comprises two tubercles and a roughened area, site for ligament and menisci attachment in the knee joint.

  • Tibial Tuberosity:

    • Located anteriorly inferior to condyles, where the patellar ligament attaches.

Shaft

  • Features three borders and three surfaces (anterior, posterior, lateral).

  • Important Borders:

    • Anterior Border:

      • Palpable as the shin, starting at tibial tuberosity; clinically prone to bruising.

    • Posterior Surface (Soleal Line):

      • Acts as the origin point for part of the soleus muscle.

    • Lateral Border (Interosseous Border):

      • Attachment for the interosseous membrane, binding the tibia to the fibula.

Distal End

  • Widens to facilitate weight-bearing; features the Medial Malleolus for ankle joint articulation.

  • Fibular Notch:

    • Notch on the lateral side where the fibula binds to the tibia.

Clinical Relevance of the Tibia

  • Fractures:

    • Common in middle-aged and elderly populations.

    • Fractures usually occur in the tibia’s middle or proximal ends, often affecting knee ligaments.

    • Medial malleolus fractures caused by forced inversion at the ankle.

The Fibula

  • Located laterally in the leg; provides muscle attachment, not weight-bearing.

  • Articulations:

  1. Proximal tibiofibular joint with tibia.

  2. Distal tibiofibular joint with fibular notch.

  3. Ankle joint with talus.

Proximal End

  • Enlarged head with a facet for tibial articulation.

  • Common fibular nerve runs posteriorly and laterally along the neck.

Shaft

  • Three surfaces: anterior, lateral, posterior; aligns with the leg's three compartments.

Distal End

  • Lateral Malleolus:

    • More prominent than the medial malleolus, palpable laterally at the ankle.

Clinical Relevance of the Fibula

  • Fractures: Specifically the lateral malleolus due to forced external rotation or eversion.

The Foot

  • Comprised of 26 bones categorized into three groups:

  1. Tarsals: Seven irregular bones in the ankle area.

  2. Metatarsals: Five bones connecting tarsals to phalanges.

  3. Phalanges: Toes contain three phalanges (except big toe which has two).

Tarsal Details

  • Organized into proximal, intermediate, and distal groups.

  • Proximal Group: Talus and calcaneus forming the ankle area.

    • Talus: Transmits tibial forces to the calcaneus with no muscle attachments.

    • Calcaneus: Main weight-bearing bone, with notable articulations including the subtalar and calcaneocuboid joints.

Intermediate & Distal Groups

  • Intermediate: Navicular bone articulating with talus and cuneiforms.

  • Distal: Cuboid and three cuneiforms forming the metatarsal connections.

The Knee Joints

  • Structure: Bicondylar synovial joint supporting flexion, extension, and slight rotation.

  • Articulations:

    • Tibiofemoral and patellofemoral joints forming the primary knee joint structure.

  • Menisci: C-shaped fibrocartilage structures enhancing stability and shock absorption.

Clinical Relevance of Knee Injuries

  • Collateral Ligaments: Commonly injured by lateral forces impacting stability.

  • Cruciate Ligaments: Anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) injuries notably from hyperextension or direct blow.

  • Bursae Inflammation: Resulting from friction leading to common syndromes like housemaid’s knee.

The Ankle Joints

  • Structure: Talocrural joint formed by the tibia, fibula, and talus; mainly allows dorsiflexion and plantarflexion.

  • Ligaments:

  1. Medial Ligament: Stabilizes against eversion.

  2. Lateral Ligament: Stabilizes against inversion.

Movements and Muscles

  • Dorsiflexion: Contraction of anterior compartment muscles.

  • Plantarflexion: Involves muscles from the posterior compartment.

Muscles of the Lower Limb

Anterior Compartment

  • Major Muscles:

    • Tibialis anterior, extensor digitorum longus, extensor hallucis longus.

  • Function: Dorsiflexion and toe extension.

  • Innervation: Deep fibular nerve.

Lateral Compartment

  • Major Muscles:

    • Fibularis longus and brevis.

  • Function: Eversion of the foot.

  • Innervation: Superficial fibular nerve.

Posterior Compartment

  • Superficial Muscles: Gastrocnemius, plantaris, soleus.

  • Deep Muscles: Popliteus, tibialis posterior, flexor digitorum longus, flexor hallucis longus.

  • Function: Plantarflexion and foot inversion.

  • Innervation: Tibial nerve.

Clinical Relevance: Foot Drop

  • Indicated by anterior compartment paralysis, often from common fibular nerve damage resulting in permanent plantarflexed position.

  • Patients may adopt an 'eversion flick' to compensate while walking.

Intrinsic Muscles of the Foot

  • Extrinsic Muscles: Control main foot movements (dorsiflexion, plantarflexion).

  • Intrinsic Muscles: Fine motor control for individual toe movement.

  • Layers of Intrinsic Muscles:

    • Four layers categorized by depth, with the first layer containing abductor hallucis, flexor digitorum brevis, and abductor digiti minimi.

    • Subsequent layers include quadratus plantae, lumbricals, flexor hallucis brevis, adductor hallucis, and interossei.

Summary

  • Understanding lower limb anatomy is critical for diagnosing and treating injuries effectively. The tibia and fibula provide structural support and act as important access points for muscle and ligament attachments essential for movement.