The Patella is the triangular-shaped kneecap bone located at the front of the knee joint. It is a sesamoid bone - a bone that develops within a tendon (the quadriceps tendon). The patella protects the knee joint from injury, improves mechanical efficiency of the quadriceps muscle (increases leverage), and articulates with the femur to form the patellofemoral joint. Dislocation or fracture of the patella is a common sports injury.

Intervertebral Discs are fibrocartilaginous pads located between adjacent vertebrae. Each disc consists of: Nucleus pulposus (inner gel-like core - absorbs compression forces) and Annulus fibrosus (outer fibrous ring - withstands tension and torsion). Functions: Shock absorption (cushion impact during walking, running, jumping), Flexibility (allow bending and twisting of the spine), and Height (discs account for ~25% of spinal column height). A herniated (slipped) disc occurs when nucleus pulposus protrudes through the annulus, pressing on nerves.

The Calcaneus (heel bone) is the largest bone in the foot and the largest of the tarsal bones. It forms the heel of the foot and bears most of the body's weight when walking. The Achilles tendon (the largest tendon in the body) attaches to the posterior surface of the calcaneus. A calcaneal (heel) fracture typically occurs from a fall from height landing on the feet.

The Furcula (wishbone) in birds is formed by the fusion of the two clavicles. In humans, the two clavicles remain as separate bones (left and right clavicle). The furcula acts as a spring in birds, storing and releasing elastic energy during flight. The human Clavicle (collarbone) is the homologous bone - it connects the sternum to the scapula and is the most commonly fractured bone in the human body, often from falling on an outstretched hand.

Rickets is a bone disease in children caused by Vitamin D deficiency (or calcium/phosphorus deficiency). Vitamin D is essential for calcium absorption. Without it, bones cannot mineralize properly, leading to soft, weak, deformed bones, bowed legs (genu varum), enlarged skull (Craniotabes), delayed tooth eruption, and rachitic rosary (beading of ribs). In adults, the same deficiency causes Osteomalacia (softening of bones). Both are prevented by Vitamin D supplementation and sunlight exposure.

Gout is a form of inflammatory arthritis caused by hyperuricaemia (excess uric acid in blood), leading to deposition of monosodium urate crystals in joints. It most commonly affects the big toe (metatarsophalangeal joint) - causing sudden, severe pain, redness, and swelling. Triggers: high-purine diet (red meat, shellfish, alcohol - especially beer), dehydration, certain medications. Treatment: anti-inflammatory drugs, colchicine, allopurinol (reduces uric acid production).

There are 7 cervical vertebrae (C1-C7) in the human neck. Almost all mammals have 7 cervical vertebrae regardless of their neck length - even a giraffe has only 7 (but much longer) cervical vertebrae. Special cervical vertebrae: C1 = Atlas (supports the skull, allows nodding - yes motion) and C2 = Axis (has the odontoid process/dens, allows rotation - no motion). The pivot joint between Atlas and Axis allows head rotation.

The Scapula (shoulder blade) is a flat, triangular bone located at the back of the shoulder. It forms part of the pectoral (shoulder) girdle along with the clavicle (collarbone). The scapula has: Glenoid cavity (articulates with the humerus to form the shoulder joint), Acromion process (articulates with the clavicle), and Coracoid process (attachment for muscles and ligaments). The scapula is embedded in muscles and has great mobility - important for arm movements.

A Pivot joint allows rotational movement only around a single axis. Examples: Atlanto-axial joint (between C1-Atlas and C2-Axis) = allows rotation of the head (shaking head 'no'). Radioulnar joint (proximal) = allows rotation of the forearm (pronation and supination). Hinge joint = flexion/extension (knee, elbow). Ball and socket = all directions (hip, shoulder). Gliding joint = sliding (wrist, ankle).

The Clavicle is commonly known as the collarbone. It is an S-shaped bone that connects the sternum (breastbone) to the scapula (shoulder blade). The clavicle is the only horizontal long bone in the body, the most commonly fractured bone in the body (often from falls on an outstretched hand), and it acts as a strut that holds the shoulder away from the chest and allows free movement of the arm. It forms the only bony connection between the upper limb and the axial skeleton.