Introduction to Anatomical Planes

Understanding anatomical planes is fundamental to describing the location of structures and, more importantly, the direction of movement within the human body. These are imaginary flat surfaces that pass through the body, dividing it into sections. All movements occur within or parallel to these planes.

A. Standard Anatomical Position Reminder:

Before discussing planes, it's crucial to recall the standard anatomical position:

• Body erect
• Feet slightly apart
• Palms facing forward
• Thumbs pointing away from the body

All descriptions of planes and movements assume the body is in this position.

B. The Three Cardinal Planes:

C. Clinical Relevance of Planes:

• Medical Imaging: Radiologists extensively use these planes to orient images (e.g., MRI, CT, ultrasound) and describe the location of pathologies.
• Surgical Planning: Surgeons plan incisions and approaches based on anatomical planes.
• Rehabilitation: Therapists describe exercises and patient movements in relation to these planes to ensure correct form and target specific muscle groups.
• Biomechanics: Researchers analyze human movement by breaking it down into components occurring in specific planes.

II. Anatomical Axes of Rotation

Movement at a joint occurs around an imaginary line called an axis of rotation. Each axis is perpendicular to the plane in which the movement occurs. Think of the axis as a pivot point around which the bone rotates.

A. The Three Major Axes:

1. Mediolateral (Transverse) Axis:
   • Orientation: Runs horizontally from side to side (left to right or right to left).
   • Relationship to Planes: Perpendicular to the sagittal plane.
   • Movements Associated: Movements that occur in the sagittal plane, such as flexion and extension.
     • Example: Bending your elbow (flexion) or straightening it (extension) occurs around a mediolateral axis passing through the elbow joint.
2. Anteroposterior (Sagittal) Axis:
   • Orientation: Runs horizontally from front to back (anterior to posterior or posterior to anterior).
   • Relationship to Planes: Perpendicular to the frontal (coronal) plane.
   • Movements Associated: Movements that occur in the frontal plane, such as abduction and adduction.
     • Example: Lifting your arm out to the side (abduction) or bringing it back to your body (adduction) occurs around an anteroposterior axis passing through the shoulder joint.
3. Vertical (Longitudinal) Axis:
   • Orientation: Runs vertically from superior to inferior (up and down).
   • Relationship to Planes: Perpendicular to the transverse (horizontal) plane.
   • Movements Associated: Movements that occur in the transverse plane, primarily rotational movements (medial/internal rotation, lateral/external rotation).
     • Example: Turning your head left and right (rotation of the neck) occurs around a vertical axis passing through the cervical spine. Rotating your arm inward or outward at the shoulder also occurs around a vertical axis.

B. Summary Table:

C. Importance of Axes:

• Biomechanics: Crucial for analyzing the mechanics of movement and understanding forces acting on joints.
• Exercise Science: Helps in designing exercises that target specific planes of motion and strengthen muscles responsible for movements around particular axes.
• Prosthetics and Orthotics: Design of artificial limbs and braces must consider the natural axes of human joint movement.

III. Classification of Anatomical Movements

Anatomical movements are typically described at synovial joints, which allow for a wide range of motion. Movements are often described in pairs, as they are opposing actions.

A. Movements in the Sagittal Plane (around a Mediolateral Axis):

1. Flexion:

• Definition: Movement that decreases the angle between two body parts. For most joints, this involves bringing the anterior surfaces closer together, or in the case of the knee and elbow, bringing posterior surfaces closer.
• Examples:
  • Shoulder: Bringing the arm forward and upward.
  • Elbow: Bending the arm, bringing the forearm closer to the upper arm.
  • Wrist: Bending the hand anteriorly towards the forearm.
  • Hip: Bringing the thigh forward and upward.
  • Knee: Bending the leg, bringing the heel towards the buttocks.
  • Trunk/Spine: Bending forward at the waist.
  • Neck: Bending the head forward, chin towards the chest.
• Key Muscles (Examples): Biceps brachii (elbow), Pectoralis major (shoulder), Iliopsoas (hip), Hamstrings (knee).

2. Extension:

• Definition: Movement that increases the angle between two body parts, effectively straightening the joint. It is generally the reverse of flexion.
• Hyperextension: Extension beyond the normal anatomical limit. This can indicate injury or hypermobility.
• Examples:
  • Shoulder: Moving the arm backward from the anatomical position.
  • Elbow: Straightening the arm.
  • Wrist: Straightening the hand with the forearm (or moving it posteriorly).
  • Hip: Moving the thigh backward.
  • Knee: Straightening the leg.
  • Trunk/Spine: Bending backward at the waist.
  • Neck: Extending the head backward.
• Key Muscles (Examples): Triceps brachii (elbow), Latissimus dorsi (shoulder), Gluteus maximus (hip), Quadriceps femoris (knee).

B. Movements in the Frontal (Coronal) Plane (around an Anteroposterior Axis):

1. Abduction:

• Definition: Movement of a limb or body part away from the midline of the body.
• Exceptions: Fingers/toes: away from the midline of the hand/foot.
• Examples:
  • Shoulder: Lifting the arm out to the side.
  • Hip: Moving the leg out to the side.
  • Fingers/Toes: Spreading them apart.
• Key Muscles (Examples): Deltoid (shoulder), Gluteus medius/minimus (hip).

2. Adduction:

• Definition: Movement of a limb or body part towards the midline of the body.
• Exceptions: Fingers/toes: towards the midline of the hand/foot.
• Examples:
  • Shoulder: Bringing the arm back towards the body from an abducted position.
  • Hip: Bringing the leg back towards the other leg from an abducted position.
  • Fingers/Toes: Bringing them together.
• Key Muscles (Examples): Pectoralis major, Latissimus dorsi (shoulder), Adductor group (thigh).

C. Movements in the Transverse (Horizontal) Plane (around a Vertical Axis):

1. Medial (Internal) Rotation:

• Definition: Rotational movement of a limb towards the midline of the body (turning the anterior surface inward).
• Examples:
  • Shoulder: Turning the arm inward so the palm faces posteriorly (if elbow bent to 90 degrees).
  • Hip: Turning the leg inward so the toes point medially.
• Key Muscles (Examples): Subscapularis, Pectoralis major (shoulder), Gluteus medius/minimus (hip).

2. Lateral (External) Rotation:

• Definition: Rotational movement of a limb away from the midline of the body (turning the anterior surface outward).
• Examples:
  • Shoulder: Turning the arm outward so the palm faces anteriorly (if elbow bent to 90 degrees).
  • Hip: Turning the leg outward so the toes point laterally.
• Key Muscles (Examples): Infraspinatus, Teres minor (shoulder), Obturator internus/externus (hip).

D. Combination Movement:

1. Circumduction:

• Definition: A combination of flexion, extension, abduction, and adduction movements, resulting in a conical movement of the distal end of a limb while the proximal end remains relatively stable. It can be seen at ball-and-socket joints.
• Examples:
  • Shoulder: Moving the arm in a circle (e.g., pitching a softball).
  • Hip: Moving the leg in a circle.
  • Wrist: Making circles with your hand.
• Key Muscles: Involves sequential activation of muscles responsible for flexion, extension, abduction, and adduction at the joint.

E. Special Movements:

These movements are typically specific to certain joints or body regions.

IV. Joint Structure and Its Influence on Movement

The design of a joint is the primary determinant of the range and types of motion. Synovial joint classification is based on the shape of articulating surfaces.

A. Functional Classification (Degrees of Freedom):

• Uniaxial: Movement in one plane around one axis (e.g., hinge, pivot).
• Biaxial: Movement in two planes around two axes (e.g., condyloid, saddle).
• Multiaxial: Movement in three or more planes around three or more axes (e.g., ball-and-socket).

B. Types of Synovial Joints and Their Movements:

C. Factors Affecting Joint Mobility:

• Articular Cartilage: Smoothness reduces friction.
• Ligaments: Connect bones; provide stability and limit excessive movement.
• Joint Capsule: Encloses the joint, providing containment.
• Muscles and Tendons: Cross the joint; provide dynamic stability.
• Bony Anatomy: Shape can restrict movement (e.g., olecranon process limits elbow extension).
• Soft Tissue Apposition: Contact of soft tissues (e.g., muscle bulk) can limit movement.
• Genetics and Age: Individual variation and decreased elasticity impact flexibility.

---

V. Clinical Scenarios: Abnormal Movements and Range of Motion

Understanding normal movements is critical for identifying pathologies. Deviations from normal range or pain are significant indicators.

A. Limitations in Range of Motion (ROM):

B. Abnormal Movement Patterns:

1. Compensation: Using alternative muscles/body parts due to weakness (e.g., elevating shoulder to assist arm abduction).
2. Ataxia: Incoordination; staggering gait (cerebellar dysfunction).
3. Dyskinesia: Involuntary, repetitive, bizarre movements.
4. Tremor: Rhythmic, oscillatory movement.
5. Spasticity/Rigidity:
   • Spasticity: Velocity-dependent resistance ('clasp-knife').
   • Rigidity: Non-velocity-dependent ('lead-pipe' or 'cogwheel').
6. Flaccidity: Absence of muscle tone; limp limb.

C. Pathologies and Their Impact on Movement:

• Osteoarthritis: Degeneration leads to pain/stiffness (e.g., limited knee flexion).
• Rotator Cuff Tear: Impairs abduction and rotation.
• Ankle Sprain: Limits inversion/eversion; causes pain with weight-bearing.
• Stroke: Can lead to hemiparesis or hemiplegia.
• Scoliosis: Abnormal lateral curvature affecting trunk rotation.

---

VI. Utilizing Appropriate Anatomical Terminology

Accurate communication is paramount. Using precise terms avoids ambiguity.