Introduction
The pelvis is a strong, bony structure that connects the spine to the lower limbs. It serves multiple essential functions, including weight-bearing, movement, protection of internal organs, and attachment points for muscles. The pelvis plays a crucial role in locomotion, posture, and stability.
Bones of the Pelvis
The pelvis consists of several bones that form a ring-like structure. These bones provide support and enable movement.
Innominate Bones (Hip Bones)
Each side of the pelvis consists of a hip bone (coxal bone), which is composed of three fused bones:
- Ilium: The largest and most superior part of the hip bone.
- Features the iliac crest, which serves as an attachment site for muscles.
- Ischium: The lower, posterior part of the hip bone.
- Includes the ischial tuberosity, which bears weight when sitting.
- Pubis: The anterior portion of the hip bone.
- Connected at the midline by the pubic symphysis.
Sacrum and Coccyx
- The sacrum is a triangular bone formed by the fusion of five sacral vertebrae.
- The coccyx (tailbone) consists of fused vertebrae and provides attachment for ligaments and muscles.
Joints of the Pelvis
The pelvis contains several joints that provide stability and allow limited movement.
Sacroiliac Joint
- Type: Synovial and fibrous joint.
- Function: Connects the sacrum to the ilium, transmitting forces between the spine and legs.
Lumbosacral Joint
- Type: Cartilaginous joint.
- Function: Connects the lumbar spine to the sacrum, allowing trunk movement.
Pubic Symphysis
- Type: Cartilaginous joint.
- Function: Provides stability to the anterior pelvis and allows slight movement for shock absorption.
Pelvic Angle
The sacral angle and pelvic tilt influence posture and movement. These angles differ between individuals and affect biomechanical efficiency.
Movements of the Pelvis
The pelvis performs several key movements that contribute to posture and gait.
- Anterior Pelvic Tilt: Forward rotation of the pelvis.
- Posterior Pelvic Tilt: Backward rotation of the pelvis.
- Lateral Tilt: Elevation or lowering of one side of the pelvis.
- Pelvic Rotation: Twisting of the pelvis along a vertical axis.
Muscles of the Pelvis
Muscles attached to the pelvis contribute to stability and movement.
Hip Flexors
- Iliopsoas: Primary hip flexor.
- Rectus Femoris: Assists in hip flexion.
Hip Extensors
- Gluteus Maximus: Primary hip extensor.
- Hamstrings: Assist in hip extension.
Hip Abductors
- Gluteus Medius and Minimus: Stabilize the pelvis and control lateral movements.
Hip Adductors
- Adductor Group (Adductor Longus, Brevis, and Magnus): Control inward movement of the thigh.
Pelvic Stabilizers
- Core muscles: Transverse abdominis, obliques, and erector spinae contribute to pelvic stability.
Conclusion
The pelvis is a crucial structure for weight-bearing, stability, and movement. It acts as a bridge between the spine and lower limbs, playing a significant role in locomotion and posture. Understanding the pelvis’s bones, joints, and muscles is essential for improving movement efficiency and preventing injuries.