Kinematic Joint Movements: Definition, Types, and Importance

What are the kinematic joint movements?

Kinematic joint movements describe the specific types and directions of motion that occur at the body's synovial joints, focusing on the observable displacement of bones without considering the forces that produce them. Understanding these movements is fundamental to analyzing human motion, designing effective exercise programs, and diagnosing musculoskeletal issues.

Understanding Kinematics in Human Movement

Kinematics is a branch of mechanics that deals with the description of motion. In the context of human anatomy and exercise science, joint kinematics refers to the ways in in which bones move relative to each other at a joint. This includes the range of motion, the speed of movement, and the acceleration, all described without reference to the muscles or external forces involved.

Joint movements are typically classified based on the anatomical planes in which they occur and the axes around which they rotate. The human body is capable of a wide array of motions, each contributing to our ability to perform daily tasks, engage in sports, and maintain posture.

Planes of Motion and Axes of Rotation

To accurately describe kinematic joint movements, it's essential to understand the three cardinal anatomical planes and their corresponding axes of rotation:

• Sagittal Plane / Mediolateral (Frontal) Axis: This plane divides the body into left and right halves. Movements in the sagittal plane occur around a mediolateral (or frontal) axis, which passes horizontally from side to side.
  • Primary Movements: Flexion, Extension, Hyperextension, Dorsiflexion, Plantarflexion.
• Frontal (Coronal) Plane / Anteroposterior (Sagittal) Axis: This plane divides the body into front (anterior) and back (posterior) halves. Movements in the frontal plane occur around an anteroposterior (or sagittal) axis, which passes horizontally from front to back.
  • Primary Movements: Abduction, Adduction, Lateral Flexion (of trunk/neck), Inversion, Eversion.
• Transverse (Horizontal) Plane / Longitudinal (Vertical) Axis: This plane divides the body into upper (superior) and lower (inferior) halves. Movements in the transverse plane occur around a longitudinal (or vertical) axis, which passes vertically through the body.
  • Primary Movements: Internal (Medial) Rotation, External (Lateral) Rotation, Pronation, Supination, Horizontal Abduction, Horizontal Adduction, Protraction, Retraction.

Multiplanar Movements: Some complex movements, such as Circumduction, involve a combination of movements in all three planes, resulting in a circular or cone-shaped path.

Common Kinematic Joint Movements Explained

Here's a detailed breakdown of the most common kinematic joint movements, along with examples:

• Flexion: Decreasing the angle between two bones at a joint.
  • Examples: Bending the elbow (forearm towards upper arm), bending the knee (heel towards glutes), bringing the chin towards the chest.
• Extension: Increasing the angle between two bones at a joint, typically returning to anatomical position.
  • Examples: Straightening the elbow, straightening the knee, lifting the head to look straight ahead.
• Hyperextension: Extension beyond the anatomical position. While some joints (e.g., spine, shoulder) allow for natural hyperextension, excessive hyperextension can indicate injury or hypermobility in others.
  • Examples: Arching the back backward, extending the wrist backward.
• Abduction: Moving a limb or part away from the midline of the body.
  • Examples: Lifting the arm out to the side, spreading the fingers apart.
• Adduction: Moving a limb or part towards the midline of the body.
  • Examples: Bringing the arm back down to the side, bringing the legs together.
• Internal (Medial) Rotation: Rotating a limb around its longitudinal axis so that its anterior surface turns towards the midline of the body.
  • Examples: Turning the arm inward at the shoulder, turning the leg inward at the hip.
• External (Lateral) Rotation: Rotating a limb around its longitudinal axis so that its anterior surface turns away from the midline of the body.
  • Examples: Turning the arm outward at the shoulder, turning the leg outward at the hip.
• Circumduction: A combination of flexion, extension, abduction, and adduction, resulting in a circular motion of a limb or body part.
  • Examples: Drawing a circle with the arm (at the shoulder joint), making circles with the ankle.
• Dorsiflexion: Movement of the foot upwards at the ankle joint, bringing the toes closer to the shin.
  • Example: Lifting the front of the foot off the ground while the heel remains down.
• Plantarflexion: Movement of the foot downwards at the ankle joint, pointing the toes away from the shin.
  • Example: Standing on tiptoes, pressing the gas pedal.
• Inversion: Turning the sole of the foot inward, towards the midline of the body.
  • Example: Rolling the ankle inward.
• Eversion: Turning the sole of the foot outward, away from the midline of the body.
  • Example: Rolling the ankle outward.
• Pronation (Forearm): Rotation of the forearm so that the palm faces posteriorly or downwards.
  • Example: Turning the hand to pour out a cup.
• Supination (Forearm): Rotation of the forearm so that the palm faces anteriorly or upwards.
  • Example: Turning the hand to hold a cup (as if to drink).
• Protraction: Moving a body part anteriorly (forward) in the transverse plane.
  • Examples: Pushing the shoulders forward, jutting the jaw forward.
• Retraction: Moving a body part posteriorly (backward) in the transverse plane.
  • Examples: Pulling the shoulders back, pulling the jaw back.
• Elevation: Moving a body part superiorly (upwards).
  • Examples: Shrugging the shoulders, closing the mouth.
• Depression: Moving a body part inferiorly (downwards).
  • Examples: Dropping the shoulders, opening the mouth.
• Opposition: Movement of the thumb across the palm to touch the tips of the other fingers.
  • Example: Grasping an object.
• Reposition: The reverse movement of opposition, returning the thumb to its anatomical position.

Importance in Exercise and Rehabilitation

A deep understanding of kinematic joint movements is indispensable for fitness professionals, physical therapists, and anyone interested in optimizing human performance and health.

• Exercise Prescription: Knowing the specific movements a joint can perform allows for the selection of exercises that effectively target desired muscle groups and achieve specific training goals, while respecting joint biomechanics.
• Technique Correction: Identifying deviations from proper kinematic patterns during exercise helps in correcting form, reducing the risk of injury, and maximizing exercise efficacy.
• Injury Prevention and Rehabilitation: Understanding normal joint kinematics is crucial for identifying abnormal movement patterns that may contribute to injury. In rehabilitation, exercises are designed to restore full, pain-free kinematic motion.
• Functional Movement: Daily activities, from walking to reaching, are complex combinations of these basic kinematic movements. Analyzing these movements helps improve efficiency and reduce strain in everyday life.

Conclusion

Kinematic joint movements are the fundamental building blocks of human motion. By precisely defining how bones move at joints within the anatomical planes and around specific axes, we gain a comprehensive framework for analyzing, understanding, and improving physical performance. This knowledge is not merely academic; it is a practical tool for anyone dedicated to the science of movement, whether in a clinical, athletic, or personal fitness context.