Joints of the Lower Limb

Joints of the Lower Limb

• A joint is a point of connection between two bones, where strands of connective tissue (ligaments) hold the bones together and ensure stability.

Classification of Joints

• According to structure:
  • Fibrous joints: bones united by fibrous connective tissue, no joint cavity, little or no movement.
  • Cartilaginous joints: connected by hyaline or fibrocartilage, some movement.
  • Synovial joints: joined by fluid, freely movable, articular surfaces covered by hyaline cartilage.
• According to motion capability:
  • Synarthroses: immovable joints.
  • Amphiarthroses: little movement.
  • Diarthroses: great amount of motion.

Fibrous Joints

• Types:
  • Sutures: bones interlocking, e.g., skull bones.
  • Syndesmosis: bones connected by ligaments, some movement, e.g., radioulnar syndesmosis.
  • Gomphoses: teeth and sockets of alveoli.

Cartilaginous Joints

• Types:
  • Synchondrosis: connected by hyaline cartilage, mostly temporary, e.g., epiphyseal plates.
  • Symphysis: connected by fibrocartilage, e.g., manubrium and body of sternum, symphysis pubis.

Synovial Joints

• Characteristics:
  • Joint cavity filled with synovial fluid.
  • Articular surfaces covered by hyaline cartilage.
  • Some have articular discs.
  • Joint capsule surrounds the ends of bones and forms the cavity.
  • Joint capsule has two layers: fibrous capsule and synovial membrane.
  • Synovial fluid lubricates the joint.
• Classifications:
  • Plane or gliding joints: uniaxial, e.g., intercarpal joints.
  • Pivot joints: uniaxial, e.g., head of radius and ulna.
  • Hinge joints: uniaxial, e.g., elbow and knee joints.
  • Ball and socket joints: multiaxial, e.g., hip and shoulder joints.
  • Ellipsoid joints: biaxial, e.g., atlantoccipital and radiocarpal joints.
  • Saddle joints: biaxial, e.g., first carpometacarpal joint.

Types of Movement

• Gliding: between carpal bones.
• Angular: flexion, extension, abduction, and adduction.
• Circular: rotation, supination, and pronation, circumduction.
• Special movements: elevation, depression, inversion, eversion, opposition, and reposition.

Hip Joint

• Type: ball and socket synovial joint.
• Articulation: hemispherical head of femur and cup-shaped acetabulum.
• Acetabular notch: deficient lower part of acetabulum.
• Acetabular labrum: fibrocartilaginous rim deepening the joint cavity.
• Transverse acetabular ligament: labral bridge crossing the notch.
• Joint capsule and ligaments:
  • Capsule encloses the joint.
  • Ligaments: iliofemoral, pubofemoral, ischiofemoral, and ligament of the head of femur.
• Nerve supply: femoral, obturator, sciatic, and nerve to the quadratus femoris.
• Movements:
  • Flexion: iliopsoas, rectus femoris, and sartorius.
  • Extension: gluteus maximus, hamstrings, and iliopsoas.
  • Abduction: gluteus medius, minimus, sartorius, and tensor fasciae latae.
  • Adduction: adductors, gracilis, and pectineus.
  • Lateral rotation: short lateral rotators, gluteus maximus, and iliopsoas.
  • Medial rotation: anterior fibers of gluteus medius and minimus, and tensor fasciae latae.

Knee Joint

• Type: condyloid joint.
• Articulation: tibia and femoral condyles.
• Patellofemoral joint: plane gliding joint.
• Articular surfaces covered by hyaline cartilage.
• Capsule: surrounds the sides and posterior aspect of the joint.
• Ligaments:
  • Extracapsular ligaments: ligamentum patellae, lateral collateral, medial collateral, and oblique popliteal ligaments.
  • Intracapsular ligaments: anterior and posterior cruciate ligaments, and menisci.
• Menisci: C-shaped fibrocartilage, attached to the joint capsule.

Tarsal Joints

• Types:
  • Subtalar joint: plane synovial joint, between talus and calcaneum.
  • Talocalcaneonavicular joint: plane synovial joint, between head of talus, sustentaculum tali, and posterior surface of navicula.
  • Calcaneocuboid joint: plane synovial joint, between calcaneum and cuboid.
  • Cuneonavicular joint: between navicula and three cuneiforms.
  • Cuboideonavicular joint: fibrous joint, connected by dorsal and plantar interosseous ligaments.
• Movements:
  • Inversion: tibialis anterior, extensor hallucis longus, and medial tendons of extensor digitorum longus.
  • Eversion: peroneus longus, peroneus brevis, and lateral tendons of extensor digitorum longus.

Metatarsophalangeal and Interphalangeal Joints

• Types:
  • Plane synovial joints.
  • The tarsometatarsal joint of the big toe has a separate joint cavity.
• Deep transverse ligaments connect the joints.