--- module: 076-03 language: en chapter: 76 title: "Back, Spinal Column, Upper Limb, and Lower Limb Anatomy" module_title: "Lower-limb osteology, joints, muscles, vessels, nerves, and gait integration" source_sha256: 6df26ee6c1e7f9c70fbe14687c8c79f3d74184ed9bed65b7841aa0aefda24720 --- # Lower limb anatomy and gait ## Support over mobility ### Supports weight, absorbs impact, propels, balances ### More constrained joints, more robust bones ### Aligned force from pelvis to foot ## Hip joint ### Acetabulum deepened by labrum ### Iliofemoral ligament resists hyperextension #### Upright standing with little muscle activity ### Head ligament artery matters mainly in children ### Retinacular branches from medial circumflex femoral #### Injured in intracapsular fracture #### Avascular necrosis and non-union ### Posterior dislocation through a flexed hip #### Can injure the sciatic nerve ### Hip pain refers to groin, thigh, knee ## Gluteal region and thigh ### Gluteus maximus extends, externally rotates hip ### Gluteus medius, minimus stabilise pelvis in stance #### Superior gluteal injury: contralateral pelvic drop ### Piriformis divides greater sciatic foramen #### Sciatic nerve usually exits below, varies ### Anterior compartment: femoral nerve #### Patella increases quadriceps moment arm ### Medial adductors: obturator nerve ### Hamstrings mainly tibial division #### Short head of biceps: common fibular #### Extend hip, flex knee, decelerate swing ## Femoral triangle and adductor canal ### Lateral to medial: nerve, artery, vein, lymphatics #### Femoral sheath excludes the nerve #### Femoral canal is a hernia site medial to vein ### Profunda femoris supplies the thigh ### Femoral artery through hiatus becomes popliteal #### Saphenous nerve does not pass the hiatus ### Great saphenous anterior to medial malleolus ### Small saphenous behind lateral malleolus ## Knee ### Femoral condyles roll and glide on flat plateaus ### Menisci deepen, distribute load, absorb shock #### Medial meniscus firmly attached, less mobile ### Cruciates resist anterior and posterior translation ### Tibial collateral resists valgus, blends with capsule ### Fibular collateral resists varus, separate from meniscus ### Terminal extension locks, popliteus unlocks ### Popliteal artery lies deepest in the fossa #### Reduced dislocation may hide vascular injury ## Leg compartments ### Anterior: dorsiflexion, deep fibular nerve #### Anterior tibial artery becomes dorsalis pedis ### Lateral: eversion, superficial fibular nerve ### Common fibular nerve at fibular neck #### Compression causes foot drop ### Superficial posterior plantarflex via calcaneal tendon ### Deep posterior flex toes, invert, support arches ### Tarsal tunnel behind medial malleolus #### Tibial-nerve compression ## Ankle and foot arches ### Mortise most stable in dorsiflexion #### Wider anterior talus engages mortise ### Lateral ligaments and strong deltoid ligament ### Subtalar joints adapt to terrain ### Talus: no muscle attachments, vulnerable supply ### Talar head is keystone of medial arch ### Lateral arch lower and more rigid ### Windlass mechanism tightens plantar aponeurosis ## Lumbosacral plexus ### Lumbar plexus forms within psoas #### Lateral femoral cutaneous: meralgia paraesthetica ### Sciatic nerve: tibial and common fibular divisions ### Superior gluteal abductors, inferior gluteus maximus ### Pudendal nerve supplies perineum ### Deep fibular senses first web space ## Gait integration ### Stance and swing phases alternate #### Double support disappears in running ### Hip abductors stabilise pelvis in stance ### Quadriceps control knee flexion after contact ### Plantarflexors restrain tibia, generate push-off ### Dorsiflexors control lowering, clear toes ### Deficits create compensations elsewhere ### Linked kinetic chain, not one joint