Comprehensive Upper & Lower Limb Anatomy – Muscles, Nerves, Joints & Vasculature

1. Scapular & Shoulder Musculature

• Dynamic stabilisation of the shoulder complex relies on three overlapping muscular “teams”:
- Rotator-cuff (fine-tuning, compression) – see §13
- Scapular stabilisers (position the glenoid)
- Power muscles (generate large torques)

1.1 Scapular Stabilisers

• Trapezius
• Levator scapulae
• Rhomboid major & minor
• Serratus anterior
• Pectoralis minor

1.2 Power Muscles Acting on the Shoulder Girdle

• Deltoid
• Pectoralis major
• Latissimus dorsi
• Teres major

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2. Accessory Joint Movements (Arthrokinematics)

• Glide / slide – one single point of one joint surface meets a series of new points on the opposing surface.
- Directions relevant for the GH joint: anterior, posterior, inferior.
• Roll – a series of new points on each surface meet one another (think of a tyre rolling along the road).
• Clinical pearl: combined roll + glide keeps the humeral head centred on the glenoid during overhead elevation, preventing impingement.

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3. Quadrangular Space

Boundaries ("TLST" mnemonic – Teres minor, long head of trIceps, surgical neck, Teres major):
• Superior – Teres minor
• Inferior – Teres major
• Medial – Long head of triceps brachii
• Lateral – Surgical neck of humerus
Contents:
• Axillary n.
• Posterior circumflex humeral a. & v.
• Significance: entrapment here produces \approx 11\% of non-traumatic axillary neuropathies; pain + deltoid weakness.

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4. Elbow & Proximal Forearm Articulations

4.1 Ulno-humeral (true hinge)

• Bony partners: trochlea of humerus ↔ trochlear notch of ulna.
• Motions: flexion/extension (sagittal plane).

4.2 Radio-humeral

• Capitulum of humerus ↔ head of radius.
• Provides a buttress during valgus load; little pure motion.

4.3 Proximal Radio-ulnar

• Head of radius ↔ radial notch of ulna.
• Pivot joint allowing \pronation / \supination.

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5. Prime Movers Around the Elbow & Wrist

• Elbow flexors: brachialis, biceps brachii, brachioradialis.
• Elbow extensors: triceps brachii, anconeus.
• Wrist extensors: extensor carpi radialis longus & brevis, extensor carpi ulnaris, extensor digitorum; supinator assists forearm rotation.
• Wrist flexors: flexor carpi radialis, flexor carpi ulnaris, palmaris longus, flexor digitorum superficialis; pronator teres pronates & weakly flexes.

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6. Anatomical Snuff-box

Borders (lateral ➜ medial):
• Abductor pollicis longus & Extensor pollicis brevis
• Extensor pollicis longus
Floor: scaphoid bone (≈ 70\% of carpal fractures) – tenderness here ⇒ high index of suspicion.

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7. Classical Nerve Lesions of the Upper Limb

• Median n. palsy – "Ape hand" (loss of thumb opposition), "Benediction/Bishop’s sign" on attempted fist.
• Radial n. palsy – "Wrist drop" (loss of wrist/finger extensors).
• Ulnar n. palsy – "Claw hand", "Cyclist’s palsy" (handle-bar compression in Guyon’s canal).

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8. Lumbar Plexus (L1–L4)

8.1 Iliohypogastric (L1)

• Motor – internal oblique, transversus abdominis.
• Sensory – posterolateral gluteal skin.

8.2 Ilioinguinal (L1)

• Motor: same as above.
• Sensory: upper medial thigh, genital region.

8.3 Genitofemoral (L1,2)

• Motor: cremaster.
• Sensory: scrotum / mons pubis.

8.4 Lateral Femoral Cutaneous (L2,3)

• Pure sensory: anterolateral thigh → knee (meralgia paraesthetica when entrapped under inguinal lig.).

8.5 Femoral (L2–4)

• Motor: iliacus, pectineus, sartorius, quadriceps.
• Sensory: anterior thigh, medial leg (via saphenous n.).

8.6 Obturator (L2–4)

• Motor: obturator externus, adductor magnus/longus/brevis, pectineus, gracilis.
• Sensory: medial thigh.
• Mnemonic “AAAGOP” (Adductors ×3, Gracilis, Obturator externus, Pectineus).

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9. Sacral Plexus (L4–S4)

9.1 Posterior Divisions

• Superior gluteal n. – gluteus medius/minimus, tensor fascia latae (Trendelenburg sign when weak).
• Inferior gluteal n. – gluteus maximus (stairs, rising).
• Perforating cutaneous n. – skin of inferior-medial buttock.
• Nerve to piriformis (motor).
• Pelvic splanchnic nerves (S2–S4 parasympathetic) – bladder, distal colon.

9.2 Anterior Divisions

• Nerve to obturator internus (+ sup. gemellus).
• Nerve to quadratus femoris (+ inf. gemellus).
• Pudendal n. – external sphincters, genital sensation.
• Posterior cutaneous n. of thigh – posterior thigh, lower buttock, upper calf.

9.3 Sciatic Nerve Complex

• Sciatic n. (largest) – hamstrings + HS part of adductor magnus.
- Tibial division: posterior superficial & deep compartments of leg → sural n.
- Common peroneal (fibular) division:
• Deep branch → anterior compartment.
• Superficial branch → lateral compartment.

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10. Neurological Screen (Lumbosacral Myotomes / Dermatomes / Reflexes)

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11. Lower-Extremity Arterial Tree

1. Blood exits heart via aorta → descending thoracic → abdominal aorta.

2. Bifurcation at L4 into R/L common iliac aa.

11.1 Internal Iliac Artery Branches

• Obturator a. (through obturator canal):
- Anterior branch → pectineus, obturator externus, adductors, gracilis.
- Posterior branch → deep gluteal mm.
• Superior & inferior gluteal aa. (greater sciatic foramen) – superior above piriformis, inferior below.

11.2 External Iliac → Femoral Artery Pathway

• External iliac becomes femoral a. at inguinal ligament, coursing through femoral triangle.
• Profunda femoris (deep femoral) gives perforating branches, medial & lateral femoral circumflex aa.
• Distally, femoral a. passes through adductor canal → popliteal a.

11.3 Popliteal Bifurcation (inferior border of popliteus)

• Anterior tibial a. → dorsalis pedis a.
• Posterior tibial a. → fibular (peroneal) a. + plantar branches.

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12. Venous Return of the Lower Limb

12.1 Superficial System

• Dorsal/plantar venous networks →
- Small saphenous v. (posterior leg) → popliteal v.
- Great saphenous v. (medial leg/thigh) → femoral v.

12.2 Deep System

• Digital & metatarsal vv. → posterior tibial, anterior tibial, fibular vv. → femoral → common iliac → inferior vena cava.

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13. Dynamic & Static Shoulder Stabilisers

13.1 Dynamic

• Rotator cuff “SITS” – Supraspinatus, Infraspinatus, Teres minor, Subscapularis.
• Scapular stabilisers (see §1.1).
• Power muscles (see §1.2).

13.2 Static

• Bony geometry – golf ball (humeral head) on a tee (glenoid fossa; only ≈ \frac13 coverage).
• Glenoid labrum – fibrocartilaginous rim deepening socket by \approx 50\%.
• Joint capsule – redundant inferiorly; taut superiorly.
• Glenohumeral ligs. – superior, middle, inferior complexes (often remembered as “LAC, CCCC”).

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14. Femoral Triangle

• Boundaries:
- Superior – inguinal ligament
- Lateral – sartorius
- Medial – adductor longus
• Floor: iliopsoas (lateral) + pectineus (medial).
• Contents (lat → med) “NAVEL”:
- Femoral Nerve
- Femoral Artery
- Femoral Vein
- Empty space (femoral canal)
- Lymph nodes (Cloquet’s).
• Clinical: site of arterial catheterisation; femoral hernias protrude through the canal (medial to vein).

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15. Key Clinical Pearls & Integrations

• Shoulder impingement is managed by enhancing inferior glide of the humeral head (see §2).
• A fall on an out-stretched hand (FOOSH) with snuff-box tenderness ⇒ treat as scaphoid # even if X-ray negative (retrograde blood supply).
• Entrapment of the lateral femoral cutaneous n. under tight belts = meralgia paraesthetica (burning lateral thigh pain).
• Piriformis hypertrophy may compress the sciatic n. – pain radiates L4→S3 dermatome distribution.
• Popliteal aneurysm may mimic Baker’s cyst; distal pulses (dorsalis pedis, posterior tibial) must be palpated (see §11.3).
• Great saphenous vein is harvested for CABG; incision just anterior to medial malleolus protects the saphenous n.