Skeletal Arthrology Study of the Joints PDF

Skeletal Arthrology Study of the Joints DR. DOHA AL-AFIFI Objectives Define the joint. Describe the relationship between joint mobility and joint stability. Describe the characteristics of axial motion. Describe the characteristics of nonaxial motion.  Joint Is a place or junc...

Skeletal Arthrology Study of the Joints DR. DOHA AL-AFIFI Objectives Define the joint. Describe the relationship between joint mobility and joint stability. Describe the characteristics of axial motion. Describe the characteristics of nonaxial motion.  Joint Is a place or junction between two or more bones A joint is a passive structure that allow movement to occur it does not create the movement Main types of a joint: compound joint simple joint  Functions of the joint (SASW ) The primary function of a joint is to allow movement (Mobility). The movement that occurs at a joint is created by muscles. The role of a muscle contraction is actually to create a force on the bones of a joint; that force can create movement at the joint. However, the force of the muscle contraction can also stop or modify movement. Ligaments and joint capsules function to limit excessive movement at a joint. Therefore, the following general rules can be stated: ❍ Joints allow movement. ❍ Muscles create movement. ❍ Ligaments/joint capsules limit movement.  Stability: Even though the primary function of a joint is to allow motion to occur, excessive motion would create an unstable joint. Therefore a joint must be sufficiently stable that it does not lose its integrity and become injured or dislocated. Each joint of the body finds a balance between mobility and stability. Mobility and stability are antagonistic properties: A more mobile joint is less stable; a more stable joint is less mobile.  Weight bearing : Many joints of the body are weight bearing joints—that is, they bear the weight of the body parts located above them. Almost every joint of the lower extremity and all the spinal joints of the axial body are weight-bearing joints. As a rule, weight bearing joints need to be very stable to support the weight that is borne through them. Shock absorption: Joints can function to absorb shock. This is especially important for weight-bearing joints. The primary means by which a joint absorbs shock is the cushioning effect of the fluid within the joint cavity. Terminology related to joint function A- Range of motion ( ROM ): It is the maximum amount of displacement possible at any one joint Types of range of motion: 1- Active range of motion 2- Active assistive range of motion 3- Passive range of motion B- Degree of freedom ( DOF): Is a term designed to describe joint mechanics regarding possible movements around fixed or relatively fixed axis. The rotational changes of one member of a pairs of articulating bones around one or more of three mutually perpendicular axes is termed degree of freedom , One degree or two degree or three degree or multi- degree of freedom C- closed packed position and loose packed position 1- closed-packed position. The stable, closed-packed position of a joint is usually the result of a combination of the position of the bones such that they are maximally congruent (i.e., their articular surfaces best fit each other) and the ligaments are most taut. These two factors result in a position that restricts motion and therefore increases stability. 2-The open-packed position of a joint is effectively the opposite of the closed-packed position; it is any position of the joint wherein the combination of the congruence of the bony fit is poor and the ligaments are lax, resulting in greater mobility but poorer stability of the joint. AXIAL AND NONAXIAL MOTION 1- Axial motion is a motion of a body part that occurs about or around an axis. ❍ This type of motion is also known as circular motion because the body part moves along a circular path around the axis ❍ With axial motion not every point on the body part moves the same amount. A point closer to the axis moves less (and would transcribe a smaller circle) than a point farther from the axis (which would transcribe a larger circle). ❍ In other words, with axial motion the body part moves in a circular path around the axis in such a manner that one part of the body part moves more than another part of the body part a point farther from the axis (which would transcribe a larger circle).  Every axial movement moves around an axis. An axis is an imaginary line in space around which axial motions occur.  For example, the action that is occurring would be described the following way: Flexion of the right forearm at the elbow joint. This tells us three things: 1. The direction of the action: flexion 2. The body part that is moving: the right forearm 3. At which joint the action is occurring: the right elbow joint  2- Nonaxial motion Is motion of a body part that does not occur about or around an axis. ❍ This type of motion is also known as a gliding motion because the body part glides along another body part. ❍ With nonaxial motion, every aspect of the body part moves/glides the same amount. In other words, every point on the body part moves in a linear path exactly the same amount in the same direction at the same time as every other point on the body part. ❍ With nonaxial motion the body part does not move around an axis but instead glides as a whole in a linear direction. Nonaxial motion Difference between axial and non-axial motion Axial Non-Axial  Joint Action Terminology Five major pairs of directional terms are used throughout most of the body: 1. Flexion/extension 2. Abduction/adduction 3. Right lateral flexion/left lateral flexion 4. Lateral rotation/medial rotation 5. Right rotation/left rotation The following pairs of directional terms are used for certain actions at specific joints of the body: ❍ Plantarflexion/dorsiflexion ❍ Eversion/inversion ❍ Pronation/supination ❍ Protraction/retraction ❍ Elevation/depression ❍ Upward rotation/downward rotation ❍ Anterior tilt/posterior tilt ❍ Opposition/reposition ❍ Lateral deviation to the right/lateral deviation to the left ❍ Horizontal flexion/horizontal extension ❍ Hyperextension ❍ Circumduction reverse action A reverse action is when a muscle contracts and the attachment that is usually considered to be more fixed—often termed, the origin—moves, and the attachment that is usually considered to be more mobile—often termed, the insertion—stays fixed Physiological movements vs. accessory motions Physiological movements - flexion, extension, abduction, adduction, & rotation occur by bones moving through planes of motion about an axis of rotation at joint Osteokinematic motion - resulting motion of bones relative to 3 cardinal planes from these physiological Physiological movements vs. accessory motions For osteokinematic motions to occur there must be movement between the joint articular surfaces Arthrokinematics - motion between articular surfaces Physiological movements vs. accessory motions 3 specific types of accessory motion Spin – Roll - Glide Accessory motions Roll (rock) - a series of points on one articular surface contacts with a series of points on another articular surface Glide (slide) (translation) - a specific point on one articulating surface comes in contact with a series of points on another surface Accessory Motions Spin - A single point on one articular surface rotates about a single point on another articular surface Motion occurs around some stationary longitudinal mechanical axis in either a clockwise or counterclockwise direction  Ball-and-Socket Joints Smooth hemispherical head fits within a cuplike depression head of humerus into glenoid cavity of scapula head of femur into acetabulum of hip bone Multiaxial joint