Arthrokinematics: Roll, Glide, Spin, Traction & Compression

Summary

This video explains key kinematic movements in osteokinematics, including roll, glide, spin, traction, and compression. It covers how joint surfaces move around an axis and in specific planes, with examples such as the humeral head on the glenoid. The video delves into the concave-convex rule, describing how rolling, gliding, spinning, and traction work in joint mechanics. It also emphasizes the importance of compression for joint stability and cartilage health. A helpful overview for understanding these movements, crucial for assessing joint function.

Takeaways

• 😀 Kinematics describes the movement of bones around an axis, with changes in angulation like flexion and extension.
• 😀 Osteokinematics refers to movements of joint surfaces, such as concave and convex interactions.
• 😀 Roll movement involves rotation where points on both joint surfaces make contact, and it always follows the angulating bone's direction.
• 😀 Pure rolling causes compression on the angulating side and separation on the opposite side of the joint.
• 😀 Gliding or sliding movements involve one point on a surface contacting multiple points on the opposing surface.
• 😀 Spin movements involve one point of a joint staying in contact while other points rotate around an axis.
• 😀 Traction, or distraction, separates joint partners, and it does not always align with the long axis of the bones.
• 😀 In the hip joint, traction must occur perpendicular to the concave joint's line, not along the femur’s axis.
• 😀 Compression occurs when the joint space decreases, providing stability and aiding in cartilage health through synovial fluid movement.
• 😀 Kinematic movements, including roll, glide, spin, traction, and compression, are important for understanding joint dynamics.
• 😀 The video encourages viewers to check out additional resources, including a newly released ebook and mobile app.

Q & A

What is the difference between kinematics and osteokinematics?

Kinematics refers to the movement of bones in space around an axis and in a specific plane, describing changes in angulation like flexion and extension. Osteokinematics, on the other hand, specifically describes the movement of joint surfaces of a male (convex) and female (concave) joint in relation to each other.

What does the term 'roll' mean in joint movement?

In joint movement, 'roll' refers to a rotation where new points on both joint surfaces make contact with each other. For example, when rolling to the left, point 1 of the convex surface contacts point 1 of the concave surface, point 2 of the convex surface contacts point 2 of the concave surface, and so on.

What happens during pure rolling in joints?

During pure rolling, compression occurs on the side where the bone is angulating, and separation occurs on the opposite side. However, pure rolling does not occur alone in functioning joints because without a spin or a glide, the moving joint surface would roll off the edge of its joint partner.

What is a 'glide' movement in joints?

A glide, or sliding movement, is a translation where one point on a joint surface moves to make contact with new points on the opposing surface. For instance, in the case of the convex surface, point 0 contacts points 0, 1, and 2 on the concave surface.

Can a spin occur independently in joint movement?

A pure spin is rare but can occur when one point of the moving joint stays in contact with the same point on the other joint partner, while all other points rotate around an axis. A real-world example of an impure spin is during shoulder flexion and extension where the head of the humerus spins on the glenoid.

What is 'traction' in joint movement?

Traction refers to the separation or distraction of two joint partners. It does not always occur along the long axis of the bony partners, as seen in the hip joint where traction is directed perpendicular to the joint line of the concave joint partner.

How does traction differ in the hip joint?

In the hip joint, traction does not follow the long axis of the femur. Instead, it must be perpendicular to the joint line of the concave joint partner to avoid causing an inferior glide.

What is the purpose of compression in joints?

Compression is the decrease in joint space between two partners, which typically occurs during weight-bearing. It provides stability to the joint and helps move synovial fluid, maintaining cartilage health.

Why is knowledge of kinematic movements important?

Understanding kinematic movements is essential to grasp the concave-convex rule, which helps explain the behavior of joint surfaces during movement. This knowledge aids in improving joint function and managing joint-related conditions.

What is the 'concave-convex rule' mentioned in the video?

The concave-convex rule, described by Carlton Bond, explains how the movement of a concave and convex joint partner affects the direction of joint movement. This rule helps in understanding how the surfaces interact during joint motions like flexion and extension.