Structures to know: Upper Limb and Pelvic Girdle

Appendicular Skeleton

Pelvic Girdle

The pelvic girdle forms the base of the spine and consists of two hip bones (coxal bones) that are joined in the front at the pubic symphysis and in the back to the sacrum at the sacroiliac joints. This structure supports the weight of the upper body when sitting and standing, and it serves as an attachment point for many muscles, ligaments, and tendons.

Ilium:

• Iliac crest: The prominent ridge of the ilium that can be palpated as the hip bone, serving as an important landmark in both diagnostic and therapeutic assessments.

• Sacroiliac joint: A critical joint that connects the sacrum to the ilium, which is essential for load transfer from the upper body to the lower limbs.

• Greater sciatic notch: An important anatomical feature that allows passage for the sciatic nerve and other structures.

• Posterior superior and inferior iliac spines: Bony projections that provide attachment points for ligaments and muscles associated with the lower back and gluteal region.

• Anterior superior and inferior iliac spines: Key landmarks for the assessment of hip alignment and attachment points for the inguinal ligament.

Ischium:

• Ischial tuberosity: Often referred to as the sit bones, these are the roughened areas that bear weight when sitting.

• Ischial spine: Serves as an important landmark for medical considerations, especially in pelvic examinations.

Acetabulum:

• The socket for the hip joint, formed by the fusion of the ilium, ischium, and pubis, which provides stability and movement for the hip joint.

Obturator foramen:

• A large opening for blood vessels and nerves to pass through, crucial for the innervation and vascular supply to the lower limb.

Pubis:

• Pubic symphysis: A cartilaginous joint between the left and right pubic bones, allowing for slight movement and necessary for childbirth.

• Subpubic angle: Also known as the pubic arch, significant in determining sex from skeletal remains.

• Superior and inferior rami: Extensions that contribute to the formation of the obturator foramen and provide attachment points for muscles and ligaments.

Lower Limb

Femur:

• Head: The rounded proximal end that articulates with the acetabulum of the hip bone, critical for hip joint functionality.

• Greater trochanter: A large bony prominence serving as a major site for muscle attachment, particularly for muscles involved in hip movement and stability.

• Lesser trochanter: A smaller projection located on the femur, where key muscles for hip flexion attach.

• Linea aspera: A prominent ridge found on the posterior aspect of the femur that serves as an attachment site for muscles of the thigh.

• Lateral and medial epicondyles: Bony protrusions above the knee joint that provide attachment for ligaments and muscles.

• Lateral and medial condyles: Rounded distal ends of the femur that articulate with the tibia and are crucial for knee joint stability and movement.

Patella:

• Also known as the knee cap; categorized as a sesamoid bone that protects the knee joint and enhances the leverage of thigh muscles during knee movements.

Tibia (Thick bone):

• Lateral and medial condyles: Articulate with the femur, forming the knee joint and bearing the majority of the body’s weight.

• Medial malleolus: The bony projection on the inner side of the ankle, which plays a key role in the stability of the ankle joint by articulating with the talus of the foot.

Fibula (Fine/thin):

• Head: The proximal end where muscles of the lower leg attach.

• Lateral malleolus: The outer projection of the ankle that contributes to ankle stability and articulation with the talus.

Tarsals:

• Talus: The bone that connects the foot to the leg, forming the ankle joint and articulating with both the tibia and fibula.

• Calcaneus: The heel bone, which supports the weight of the body and provides attachment for the Achilles tendon.

• Navicular: Located in front of the talus, it articulates with the cuneiforms and the cuboid, playing a crucial role in the structure of the arch of the foot.

• Medial, intermediate, and lateral cuneiform bones: These three small bones form the arch of the foot and help with weight distribution during walking.

• Cuboid: Assists in forming the lateral side of the foot, providing a surface for muscle attachment and support.

Metatarsals:

• There are five metatarsals in the foot, numbered 1 to 5 from medial to lateral. They are crucial for weight-bearing and form the arches of the foot.

Phalanges:

• The bones of the toes; each toe has three phalanges (proximal, middle, distal) except for the hallux, or big toe, which has two (proximal and distal) that facilitate movement and dexterity of the foot.