10 Questions
What is the primary role of the hip abductor muscles during single limb stance?
To oppose the hip adductor moment produced by gravity
Which of the following statements about the forces in the hip joint is correct?
The horizontal force of the femur on the pelvis is equal to the body weight, and the vertical force is 2.5 times as much
During the stance phase of gait, the force required in the abductor muscles to balance the body on the head of the weight-bearing femur is approximately:
Twofold the body weight
What is the primary reason for the compression forces experienced by the hip joint during single limb stance, walking, or running?
The abductor muscle force exceeding the body weight
In the free-body diagram analysis of the hip joint, what does the symbol $\theta$ represent?
The angle between the abductor muscle line of action and the y-axis
Which of the following statements about the hip joint is incorrect?
It is a hinge joint that primarily allows flexion and extension
What is the approximate range of hip abduction and adduction in degrees?
0-30°
Which of the following statements about the pelvic girdle is correct?
It consists of the two hip bones and the sacrum
What is the approximate range of hip flexion and extension in degrees?
0-140°
Which of the following activities would result in the highest load on the hip joint?
Stumbling or falling
Study Notes
Biomechanics Fundamentals
- Biomechanics has 9 fundamental principles:
- Force-Motion Principle: Unbalanced forces acting on objects or bodies create or modify movement
- Force-Time Principle: Both force and time affect motion
- Range of Motion Principle: Increasing range of motion can increase speed or slow down from high speeds
- Balance Principle: Controlling body position relative to a base of support
- Coordination Principle: Timing of muscle actions and body segment motions in human movement
- Segmental Interaction Principle: Forces transferred through linked rigid bodies and joints
- Optimal Projection Principle: Optimal range of projection angles for specific goals
- Spin Principle: Rotations imparted to projectiles
- Inertia Principle: Property of objects to resist changes in their state of motion
Elements of Biomechanics
- Dynamics: Studying systems in motion with acceleration and deceleration
- Kinematics: Describing the effect of forces on a system, including motion patterns, velocity, and acceleration
- Kinetics: Studying what causes motion, including forces and moments
- Statics: Studying systems in equilibrium, either at rest or moving at a constant velocity
Newton's Laws of Motion
- Newton's First Law (Law of Inertia): Objects at rest or in motion remain so unless acted upon by an external force
- Newton's Second Law (Law of Momentum or Law of Acceleration): Force equals mass times acceleration
- Newton's Third Law: Every action has an equal and opposite reaction
Human Joints
- Anatomical Reference Planes: Three imaginary perpendicular planes dividing the body into halves by mass
- Sagittal plane: Forward and backward movements
- Frontal plane: Lateral movements
- Transverse plane: Horizontal movements
- Directional Terms:
- Superior: Towards the head
- Inferior: Away from the head
- Anterior: Towards the front of the body
- Posterior: Towards the back of the body
- Medial: Towards the midline of the body
- Lateral: Away from the midline of the body
- Proximal: Closest to the trunk
- Distal: Away from the trunk
- Superficial: Towards the surface of the body
- Deep: Away from the surface
- Mediolateral axis: Imaginary line around which sagittal plane rotations occur
- Anteroposterior axis: Imaginary line around which frontal plane rotations occur
- Longitudinal axis: Imaginary line around which transverse plane rotations occur
Types of Joints
-
- Coracoclavicular joint: Syndesmosis with the coracoid process of the scapula and the inferior surface of the clavicle
-
- Acromioclavicular joint: Between the acromion process of the scapula and the distal end of the clavicle
-
- Sternoclavicular joint: At the proximal clavicle with the manubrium or top most portion of the sternum
-
- Scapulothoracic joint: False joint where the shoulder blade glides against the thorax
Hip Joint and Loads
- Ball-and-socket joint with a high degree of stability and excellent range of movements
- Articulation between the spherical head of the femur and the concave acetabulum of the pelvis
- Pelvic girdle: Two hip bones + sacrum, allowing for rotation forward, backward, and laterally
- Flexion/extension: 0-1400, hyperextension: 0-150, abduction/adduction: 0-300, lateral/medial rotation: 0-450
- Neck of femur ~1350 to the shaft, 3 DOF with 3 mutually perpendicular axes
- Transverse axis: Lies in the frontal (coronal) plane and controls flexion/extension
- Anterior/posterior axis: Lies in the sagittal plane and controls adduction/abduction
- Vertical axis: Coincides with the long axis of the limb when the hip joint is in neutral position, controls internal and external rotation
- Major weight-bearing joint, supporting 1/3 of body weight during upright standing and more during movement
- Forces in the hip joint:
- Body weight
- Tension in large, strong hip muscles
- Impact forces translated upward
- Abductor muscle force exceeding body weight during stance, walking, or running
Test your knowledge on biomechanics fundamental principles including Force-Motion Principle, Force-Time Principle, mechanics of hard tissues, mechanics of soft tissues, and blood rheology. Learn about human joints mechanics and the basics of biomechanics.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
