3.6 Bones, Muscles & Joints of the Arms, Hands, Legs & Feet
Key Takeaways
- The arm has one upper bone, the humerus, and two forearm bones: the ulna on the little-finger side and the radius on the thumb side.
- Each hand contains 27 bones — 8 carpals in the wrist, 5 metacarpals in the palm, and 14 phalanges in the digits.
- Pronators turn the hand palm-down and supinators turn it palm-up; flexors bend the wrist and close the fingers while extensors straighten them, and abductors separate the fingers while adductors draw them together.
- Each foot contains 26 bones — 7 tarsals, 5 metatarsals, and 14 phalanges — with the talus, calcaneus, navicular, cuboid, and three cuneiforms making up the tarsal group.
- The tibialis anterior lifts the foot and turns it inward, the gastrocnemius and soleus flex the foot downward, and the peroneus longus and brevis evert the foot and turn it outward.
Where This Shows Up in Practice
A manicure includes hand and arm massage; a pedicure includes foot and lower-leg massage. Both are listed in the NIC content outlines under nail care principles and procedures, and both require you to know which structures tolerate pressure and which do not. Pressing directly on the carpals of a client with carpal tunnel syndrome, or working aggressively over the medial malleolus of a diabetic client, converts a relaxing service into an injury.
Bones of the Shoulder, Arm, and Hand
| Bone | Location | Notes |
|---|---|---|
| Clavicle | Collarbone; joins sternum to scapula | Superficial and easily bruised |
| Scapula | Shoulder blade | Controlled by the trapezius |
| Humerus | Uppermost and largest bone of the upper arm | One bone only |
| Ulna | Inner forearm bone, on the little-finger side | Its upper end forms the point of the elbow |
| Radius | Outer forearm bone, on the thumb side | Rotates over the ulna in pronation |
| Carpals | 8 small irregular bones of the wrist | Held together by ligaments |
| Metacarpals | 5 long slender bones of the palm | One per digit |
| Phalanges | 14 bones of the digits — three per finger, two in the thumb | Singular: phalanx |
Total bones in the hand and wrist: 8 + 5 + 14 = 27.
Muscles of the Arm and Hand
The muscles fall into functional pairs, and the exam tests the pair relationships more than individual names.
| Group | Action | Example |
|---|---|---|
| Flexors | Bend the wrist, draw the hand up, close the fingers | Flexor digitorum |
| Extensors | Straighten the wrist, hand, and fingers | Extensor digitorum |
| Pronators | Turn the hand palm downward | Pronator teres |
| Supinators | Turn the hand palm upward | Supinator |
| Abductors | Separate the fingers | Abductor digiti minimi |
| Adductors | Draw the fingers together | Adductor pollicis |
A memory hook that survives exam pressure: abductors move away, adductors add the fingers back together. Abductors and adductors are located at the base of each digit.
Three upper-arm muscles complete the set:
- Biceps — the two-headed muscle at the front of the upper arm; lifts the forearm and flexes the elbow.
- Triceps — the three-headed muscle covering the entire back of the upper arm; extends the forearm.
- Deltoid — large triangular muscle covering the shoulder joint; lifts and turns the arm.
Bones of the Lower Leg and Foot
| Bone | Location |
|---|---|
| Femur | Thigh — the longest bone in the body |
| Patella | Kneecap |
| Tibia | Larger, inner shin bone; forms the medial malleolus at the ankle |
| Fibula | Smaller, outer lower-leg bone; forms the lateral malleolus |
| Tarsals | 7 ankle bones: talus, calcaneus (heel), navicular, cuboid, and three cuneiforms |
| Metatarsals | 5 long bones of the instep |
| Phalanges | 14 toe bones — three per toe, two in the great toe |
Total bones in the foot: 7 + 5 + 14 = 26. Contrast this with the 27 in the hand and wrist — the two counts are a favorite distractor pair.
Muscles of the Lower Leg and Foot
| Muscle | Action | Massage Relevance |
|---|---|---|
| Tibialis anterior | Covers the front of the shin; lifts the foot and turns it inward | Often tender in clients who stand all day |
| Gastrocnemius | Superficial calf muscle; flexes the foot downward (plantar flexion) | The bulk of the calf massage |
| Soleus | Beneath the gastrocnemius; bends the foot down | Deeper, slower pressure |
| Peroneus longus | Covers the outer side of the calf; everts the foot and turns it outward | Runs along the fibula |
| Peroneus brevis | Originates on the lower fibula; everts the foot and turns it outward | Works with peroneus longus |
| Extensor digitorum longus | Front of the leg; bends the foot up and extends the toes | Superficial over the instep |
| Flexor digitorum brevis | Sole of the foot; moves the toes and helps maintain balance | The plantar surface worked in pedicure massage |
| Abductor and adductor hallucis | Move and stabilize the great toe | Relevant to bunion-prone clients |
Joints and Safe Pressure
A joint is where two or more bones meet. Cosmetologists work over hinge joints (elbow, knee, interphalangeal joints of the fingers and toes) and gliding joints (carpals, tarsals). Two working rules follow:
- Never force a joint through its range of motion. Rotation during hand or foot massage is passive and gentle; the client's own tissue sets the limit.
- Never apply deep pressure directly over a bony prominence — the malleoli at the ankle, the olecranon at the elbow, the metacarpal and metatarsal heads. Work the muscle bellies around them.
For clients with diabetes mellitus, peripheral neuropathy, or peripheral arterial disease, reduce pressure further and stop at the first sign of skin change. Section 8.5 covers the full contraindication set for foot services.
How many bones are in the human hand and wrist, and how are they distributed?
Which forearm bone lies on the thumb side, and which muscle group turns the hand palm downward?
During a pedicure massage, which muscle group flexes the foot downward and forms the bulk of the calf?