3.3 Bones, Muscles, Joints, Blood Vessels & Nerves of the Arms, Hands, Legs & Feet

Core Knowledge: The hand contains 27 bones and the foot contains 26 bones. Massage pressure is usually directed from a muscle's insertion toward its origin, which on the limbs also follows the return of venous blood toward the heart. The median nerve traverses the carpal tunnel; its compression causes carpal tunnel syndrome. The radial artery and ulnar artery furnish the principal blood supply to the hand, while the anterior tibial (dorsalis pedis) and posterior tibial arteries supply the foot. The foot is lifted by the tibialis anterior and pointed by the gastrocnemius and soleus, and most extremity joints are hinge or condyloid synovial joints.

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1. Skeletal Anatomy of the Upper & Lower Extremities

Bones provide the rigid internal framework, protect delicate neurovascular bundles, produce erythrocytes within red bone marrow, store calcium, and serve as mechanical levers for muscular contraction.

+--------------------------------------------------------------------------+
|                       SKELETAL COMPARISON TABLE                          |
|                                                                          |
|  UPPER EXTREMITY (Hand/Arm)             LOWER EXTREMITY (Foot/Leg)       |
|  --------------------------             --------------------------       |
|  Humerus (Upper arm) - 1                Femur (Thigh) - 1                |
|  Ulna (Medial forearm) - 1              Patella (Kneecap sesamoid) - 1   |
|  Radius (Lateral forearm) - 1           Tibia (Medial shin bone) - 1     |
|  Carpals (Wrist) - 8                    Fibula (Lateral slender bone) - 1|
|  Metacarpals (Palm) - 5                 Tarsals (Ankle/Heel) - 7         |
|  Phalanges (Fingers) - 14               Metatarsals (Instep) - 5         |
|                                         Phalanges (Toes) - 14            |
|  Total per Hand/Arm: 30                 Total per Foot/Leg: 30           |
+--------------------------------------------------------------------------+

Bones of the Upper Extremity (Hand, Wrist, and Arm)

• Humerus: The longest and largest bone of the upper extremity, extending from the glenohumeral joint at the shoulder to the elbow.
• Ulna: The larger, longer medial bone of the forearm (on the side of the little finger / pinky). Its proximal end forms the prominent olecranon process (the elbow point) which articulates with the humerus.
• Radius: The shorter, lateral bone of the forearm (on the side of the thumb). The disc-shaped radial head articulates with the capitulum of the humerus and rotates around the ulna, producing pronation and supination of the hand.
• Carpus (Wrist): Composed of 8 small, irregular carpal bones arranged in two transverse rows of four bones each, bound tightly by ligaments:
  • Proximal Row (Lateral to Medial):
    1. Scaphoid (Navicular of hand): Boat-shaped bone; most commonly fractured carpal.
    2. Lunate: Crescent / moon-shaped bone.
    3. Triquetrum (Triangular): Pyramidal bone articulating with the pisiform.
    4. Pisiform: Small, pea-shaped sesamoid bone resting on the anterior triquetrum.
  • Distal Row (Lateral to Medial): 5. Trapezium: Four-sided irregular bone articulating with Metacarpal I (the thumb saddle joint). 6. Trapezoid: Wedge-shaped bone articulating with Metacarpal II. 7. Capitate: The largest of all carpal bones, situated centrally as the keystone of the wrist. 8. Hamate: Wedge-shaped bone featuring a prominent hook-like anterior projection (uncinate process / hook of hamate).
• Metacarpus (Palm): 5 miniature long bones numbered I through V starting laterally at the thumb (Metacarpal I) through the pinky (Metacarpal V).
• Phalanges of the Hand (Digiti): 14 bones forming the fingers:
  • The thumb (pollex) has only 2 phalanges: proximal and distal.
  • Digits II through V (index, middle, ring, and little finger) each have 3 phalanges: proximal, middle, and distal.

Bones of the Lower Extremity (Foot, Ankle, and Leg)

• Patella: The kneecap; a large triangular sesamoid bone embedded within the quadriceps femoris tendon that protects the anterior knee joint.
• Tibia: The shin bone; the larger, primary weight-bearing medial bone of the lower leg. Its distal medial projection forms the medial malleolus (the prominent inner ankle bone).
• Fibula: The slender, non-weight-bearing lateral bone of the lower leg. It runs parallel to the tibia and stabilizes the ankle; its distal lateral projection forms the lateral malleolus (the outer ankle bone).
• Tarsus (Ankle and Rearfoot): Composed of 7 tarsal bones:
  1. Talus (Astragalus): The ankle bone. Articulates superiorly with the tibia and fibula at the talocrural joint, transmitting the entire body's weight downward to the foot.
  2. Calcaneus: The heel bone. The largest and strongest bone of the foot, projecting posteriorly to bear weight and serve as the insertion site for the massive Achilles tendon (tendo calcaneus).
  3. Navicular: Boat-shaped bone positioned on the medial foot between the talus and the cuneiforms.
  4. Medial Cuneiform (First): Wedge-shaped bone on the medial foot articulating with Metatarsal I.
  5. Intermediate Cuneiform (Second): Smallest cuneiform articulating with Metatarsal II.
  6. Lateral Cuneiform (Third): Wedge-shaped bone between the intermediate cuneiform and the cuboid, articulating with Metatarsal III.
  7. Cuboid: Cube-shaped bone located on the lateral foot anterior to the calcaneus.
• Metatarsus (Instep): 5 metatarsal bones numbered I through V from the medial big toe to the lateral small toe, forming the longitudinal and transverse arches.
• Phalanges of the Foot: 14 bones forming the toes:
  • The great toe (hallux) has only 2 phalanges: proximal and distal.
  • Toes II through V each have 3 phalanges: proximal, middle, and distal.

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2. Muscular System Architecture & Biomechanics

Muscles are specialized contractile tissues that generate mechanical tension, produce movement, maintain posture, and generate body heat.

Structural Divisions of Muscle

Every skeletal muscle consists of three anatomical sections:

1. Origin: The fixed attachment, the end of the muscle that does not move when it contracts; on the limbs it is usually the proximal end.
2. Belly: The middle, fleshy, thick contractile portion containing active actin and myosin myofibrils.
3. Insertion: The distal, movable attachment anchored to the bone, tendon, or fascia that moves when the muscle contracts.

   [ ORIGIN ] (Fixed attachment to stable proximal bone)
        |
        v
   [ BELLY ]  (Contractile muscular body)
        |
        v
   [ INSERTION ] (Movable attachment to distal bone/tendon)

   >>> USUAL MASSAGE PRESSURE DIRECTION: INSERTION ---> ORIGIN <<<

Massage Direction: Insertion to Origin

In massage manipulations such as effleurage and petrissage, pressure is usually directed from the insertion toward the origin of the muscle. Expect exam items to test this direction and the definitions of origin and insertion.

• Why it helps circulation: Veins and lymphatic vessels are low-pressure vessels with one-way valves that return fluid toward the heart. On the arms and legs, a muscle's insertion is usually farther from the body than its origin, so insertion-to-origin strokes move in the same direction as venous and lymphatic return.
• How to apply it: On the forearm and lower leg, work from the wrist or ankle up toward the elbow or knee, keep pressure within the client's comfort, and use lighter pressure over bony areas.

Primary Functional Muscle Groups of Forearms, Hands, and Legs

• Flexors: Muscles located on the anterior / volar compartment of the forearm that contract to bend the wrist and curl the fingers forward toward the palm (e.g., flexor carpi radialis, flexor digitorum).
• Extensors: Muscles located on the posterior / dorsal compartment of the forearm that contract to straighten the wrist and open the fingers backward (e.g., extensor carpi radialis, extensor digitorum).
• Pronators: Muscles of the anterior forearm (pronator teres and pronator quadratus) that turn the forearm and hand inward, causing the palm to face downward or backward.
• Supinators: Muscles (supinator muscle, assisted by biceps brachii) that rotate the radius outward, turning the palm upward or forward.
• Abductors: Muscles that draw the fingers or toes outward away from the central midline of the hand or foot (e.g., abductor pollicis, dorsal interossei).
• Adductors: Muscles that draw the fingers or toes inward together toward the central midline of the hand or foot (e.g., adductor pollicis, palmar interossei).

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3. Circulatory Pathways of the Extremities

The vascular system delivers oxygenated blood and nutrients via arteries and arterioles, exchanges gases at capillaries, and collects deoxygenated blood through venules and veins.

                        ARTERIAL SUPPLY PATHWAY

   UPPER EXTREMITY                              LOWER EXTREMITY
   ----------------                             ----------------
   Brachial Artery                              Popliteal Artery
         |                                            |
         +------------+                               +------------+
         |            |                               |            |
         v            v                               v            v
   Radial Artery   Ulnar Artery                 Anterior Tibial  Posterior Tibial
   (Thumb side /   (Pinky side /                      |          (Calf to Medial
    Snuffbox)       Palmar arches)                    v           Malleolus/Sole)
         |            |                         Dorsalis Pedis         |
         +-----+------+                         (Instep of foot)       v
               |                                      |          Plantar Arteries
               v                                      +-----+----------+
        Digital Arteries                                    | 
       (Lateral/Medial Bed)                                 v
                                                      Digital Arteries

Arterial Network of the Hand and Arm

• Brachial Artery: The principal artery of the upper arm. At the cubital fossa (elbow crease), it bifurcates into the radial and ulnar arteries:
  1. Radial Artery: Descends along the lateral (thumb) side of the forearm into the wrist. It courses through the anatomical snuffbox and forms the deep palmar arch. The radial artery is the primary anatomical site for taking a client's radial pulse at the anterior lateral wrist.
  2. Ulnar Artery: Descends along the medial (pinky) side of the forearm into the palm, forming the superficial palmar arch.
  3. Digital Arteries: Arise from the anastomotic palmar arches, traveling along the lateral and medial borders of each finger to supply dense capillary networks to the nail bed, matrix, and hyponychium.

Arterial Network of the Foot and Leg

• Popliteal Artery: Located posterior to the knee, dividing into:
  1. Anterior Tibial Artery: Descends down the anterior lower leg between the tibia and fibula, passes over the anterior ankle joint, and becomes the dorsalis pedis artery (dorsal artery of the foot). Supplies the top of the foot and dorsal digital branches to the toes.
  2. Posterior Tibial Artery: Descends deep along the posterior calf muscles, courses immediately behind the medial malleolus (where its pulse can be palpated), and enters the sole of the foot. It bifurcates into the medial and lateral plantar arteries, forming the plantar arch which supplies plantar digital arteries to the toes and nail units.

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4. Nervous System & Neurological Pathologies

The peripheral nervous system transmits sensory information from cutaneous mechanoreceptors to the central nervous system and conveys motor commands to skeletal muscles.

Peripheral Nerves of the Hand and Arm

• Radial Nerve: Traverses the lateral arm and forearm. Supplies sensory innervation to the skin of the thumb, back of the hand, and dorsal surfaces of the index and middle fingers, as well as motor control to forearm extensor muscles.
• Median Nerve: Descends down the midline of the anterior forearm and passes into the hand through the carpal tunnel beneath the fibrous flexor retinaculum. It provides sensory innervation to the palmar skin of the thumb, index finger, middle finger, and lateral half of the ring finger, as well as motor innervation to the thenar muscles.
• Ulnar Nerve: Runs along the medial arm, passes superficially through the cubital tunnel at the elbow (the "funny bone"), and enters the palm via Guyon's canal. It supplies sensation to the little finger, the medial half of the ring finger, and the medial palm.
• Digital Nerves: Terminal sensory branches supplying the fingertips, perionychium, and nail bed.

Carpal Tunnel Syndrome (CTS) in Nail Technicians

Carpal Tunnel Syndrome is an entrapment neuropathy caused by compression of the median nerve inside the narrow carpal tunnel of the anterior wrist.

• Etiology in Manicurists: Prolonged, repetitive wrist flexion and extension, awkward pinch gripping of heavy abrasive files, sustained static muscle load, and chronic mechanical vibration from handheld electric files (e-files).
• Symptoms: Paresthesia (numbness, "pins and needles"), burning pain, and nocturnal tingling radiating into the thumb, index, middle, and ring fingers. If untreated, it progresses to permanent muscle atrophy of the thenar eminence (the muscular pad at the base of the thumb) and loss of grip strength.

Peripheral Nerves of the Foot and Leg

• Tibial Nerve: A major division of the sciatic nerve descending the posterior calf into the foot behind the medial malleolus; supplies motor innervation to calf flexors and sensory innervation to the sole of the foot.
• Common Peroneal (Fibular) Nerve: Winds superficially around the neck of the fibula; bifurcates into:
  • Deep Peroneal Nerve: Extends down the anterior shin, innervating foot dorsiflexors and sensory skin between the first and second toes.
  • Superficial Peroneal Nerve: Descends along the lateral calf, supplying the lateral peroneal muscles and sensory skin across the dorsum (top) of the foot and toes.

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5. Arm, Hand, Lower Leg & Foot Muscles to Know

Upper Arm and Hand

• Deltoid: the large triangular muscle covering the shoulder; lifts and turns the arm.
• Biceps: the front of the upper arm; bends (flexes) the elbow and turns the palm upward.
• Triceps: the back of the upper arm; straightens (extends) the elbow.
• Opponens pollicis (opponent muscle of the thumb): in the palm; draws the thumb toward the fingers so the hand can grasp.
• Abductors and adductors: spread the fingers apart and draw them back together (described in Part 2).

Lower Leg

Foot

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6. Joints of the Arms, Hands, Legs & Feet

A joint is where two or more bones meet. Ligaments connect bone to bone, and tendons connect muscle to bone. Most joints in the extremities are synovial joints, cushioned by cartilage and lubricated by synovial fluid.

The foot's bones and ligaments form three arches — the medial longitudinal, lateral longitudinal, and transverse arches — that absorb shock and spread body weight.

Why Joints Matter in Nail Services

• Stay within comfortable range: joint movements during massage, such as flexing the fingers or circling the wrist or ankle, should never be forced past the client's comfort.
• Arthritis: clients with swollen, stiff, or painful joints need gentle pressure, good support for the hand or foot, and frequent comfort checks.
• Protect your own joints: awkward wrist and finger positions also strain the technician (Section 2.4).
• Massage contraindications such as deep vein thrombosis and varicose veins are covered in Section 7.3.