The Coxofemoral joint (from Latin: coxa = hip, femur = thigh) is the medical name for the hip joint. It is a ball and socket joint between the Head of Femur (ball) and the Acetabulum of hip bone (socket). It is a very stable joint (deeper socket than shoulder, reinforced by strong ligaments). Movements: flexion, extension, abduction, adduction, medial and lateral rotation, circumduction. Hip fractures (usually at the femoral neck) are extremely common in elderly with osteoporosis.

The Olecranon process is the large, bony projection at the proximal end of the Ulna - it is the pointed tip of the elbow that you can feel when you bend your arm. It forms the point of the elbow and fits into the olecranon fossa of the humerus when the arm is extended, preventing hyperextension of the elbow. The olecranon serves as an attachment point for the triceps brachii muscle (the muscle that extends the forearm).

A Herniated (Slipped/Prolapsed) Disc occurs when the nucleus pulposus (inner gel-like core) of an intervertebral disc protrudes through a tear in the annulus fibrosus (outer ring), compressing nearby spinal nerves. Most common at: L4-L5 and L5-S1 levels (lumbar spine) causing Sciatica (pain radiating down the leg), and C5-C6 level (cervical spine) causing neck and arm pain. Symptoms: sharp radiating pain, numbness, tingling, and weakness. Treatment: physiotherapy, pain management, and surgery if severe.

The forearm (between elbow and wrist) is formed by two bones: Radius (on the thumb side/lateral/outer side of the forearm) and Ulna (on the little finger side/medial/inner side of the forearm). The proximal radioulnar joint allows pronation (palm facing down) and supination (palm facing up). Similarly, the leg has two bones - Tibia (medial, larger) and Fibula (lateral, smaller) between knee and ankle.

The Clavicle (Latin: clavicula = little key) is the medical term for the collarbone. It is a slender, S-shaped long bone that connects the sternum (medially) to the acromion of scapula (laterally), is the only bony connection between the upper limb skeleton and the axial skeleton, is the most commonly fractured bone in the body, and acts as a strut to keep the shoulder elevated and away from the chest. A clavicle fracture typically occurs from a fall on an outstretched hand (FOOSH) or direct blow to the shoulder.

The knee has two cruciate ligaments (named for their cross-shaped arrangement): Anterior Cruciate Ligament (ACL) = prevents anterior (forward) displacement of tibia relative to femur. The most commonly injured knee ligament (especially in sports - football, basketball, skiing). Posterior Cruciate Ligament (PCL) = prevents posterior (backward) displacement of tibia. The knee also has: Medial (MCL) and Lateral (LCL) collateral ligaments (prevent side-to-side movement) and Medial and Lateral menisci (fibrocartilage shock absorbers).

The Patella (kneecap) is the largest sesamoid bone in the human body. It develops within the quadriceps femoris tendon and sits at the front of the knee joint. The patella increases the mechanical advantage (leverage) of the quadriceps muscle, protects the knee joint from direct impact, and reduces friction between the quadriceps tendon and femur. It articulates with the femur at the patellofemoral joint. The Pisiform is the smallest carpal (wrist) bone and is also a sesamoid bone (within the flexor carpi ulnaris tendon).

At birth, a baby has approximately 270-300 bones in the entire body (not just the skull). The skull bones in infants are not yet fully fused - many bones are still in cartilaginous form or are separate ossification centres that gradually fuse. The skull has fontanelles (soft spots) where bones have not yet joined. By adulthood, the total bone count reduces to 206 as many bones fuse together through a process called synostosis during development.

Compact bone is organized into structural units called Osteons (Haversian systems). Each osteon consists of: Haversian canal (central canal containing blood vessels and nerves), Concentric lamellae (rings of bone matrix surrounding the Haversian canal), Lacunae (small spaces containing osteocytes between lamellae), and Canaliculi (tiny channels connecting lacunae to allow nutrient exchange). Volkmann's canals run perpendicular to Haversian canals, connecting them to the periosteum and endosteum. This organization gives compact bone its great strength.

The Pelvic Girdle consists of two hip bones (os coxae / innominate bones). Each hip bone is formed by the fusion of three bones: Ilium (large, fan-shaped upper part), Ischium (lower and posterior part - the sitting bone), and Pubis (anterior/front part). These three bones meet at the Acetabulum - the cup-shaped socket that articulates with the femur head to form the hip joint. The two pubic bones meet at the pubic symphysis in the front.