Joints Flashcards
Joint
- The junction between two bones. Joints are classified according to their structure and degree of movement which is present. Joints have two main purposes: support and movement.
- Movement of the body as a whole occurs primarily through rotation of bones at individual joints. Joints also transfer and dissipate forces owing to gravity and muscle activation throughout the body.
Arthrology
The study of the classification, structure and function of joints. It serves as a foundation for the study of kinesiology. Aging, long-term immobilization, trauma and disease all affect the structure and ultimate function of joints. These factors also influence both the quality and quantity of movement.
Arthrokinematics
Is the study of motion occurring between joint surfaces.
Osteokinematics
Range of motion measured with a goniometer which identifies a change in the joint angle.
Joints Classification
May be classified based on their structure (i.e., the type of soft tissue that connects the bone to each other) and according to their function (i.e., the degree of movement that they allow).
Structural Classification of Joints
- (1) fibrous
- (2) cartilaginous
- (3) synovial
Fibrous Joint
Bones are held together by dense, fibrous connective tissue.
Cartilaginous Joint
Bones held together by either fibrocartilage or hyaline cartilage.
Synovial Joint
Bones are connected by a joint capsule, which is composed of two distinct layers, an outer fibrous layer and an inner synovial layer.
Functional Classification of Joints
- (1)synarthrotic
- (2) amphiarthrotic
- (3) diarthrotic
Synarthrotic Joint
Allows very little or no movement – referred to as an immovable joint. It consists of two adjacent edges of bone separated by very small amounts of fibrous tissue.
-Example: sutures of the skull, teeth in the sockets of the maxillae and mandible. Interosseous membrane of the forearm (between radius and ulna) and leg (between tibia and fibula).
Amphiarthrotic
Minimal (partial) movement is allowed. Provides a combination of relatively restrained movement and shock absorption. It consists of two adjacent bones separated by a significant amount of cartilage.
-Example: pubic symphysis, intervertebral discs and the vertebral body of the vertebra, and the manubriosternal joint.
Diarthrosis
Freely movable joint that allows a significant amount of movement. It represents a true joint space filled with synovial fluid and surrounded by a joint capsule. The articular surfaces are not directly bound to each other.
-Example: majority of joints of the extremities.
Structure and function of Joints
Combining both properties of structure and function: fibrous joints are synarthrotic joints, cartilaginous joints are amphiarthrotic and synovial joints are diathrotic.
Articular Cartilage
The articular or weight bearing surfaces of the bones are covered with cartilage which is resilient and functions to absorb shock and prevents direct wear and tear on the bones.
Synovial Membrane
Secretes synovial fluid into the joint cavity. The fluid provides nourishment to the articular cartilages and lubricates the joint. Under normal circumstances, there is only a small quantity of fluid present in the joint. When the synovial membrane is irritated a large quantity may be produced leading to edema.
Joint Capsule
A ligamentous sleeve which is attached firmly to both bones of the joint forming a completely enclosed capsule.
Classification of Diarthrodial Joints
- (1) uniaxial
- (2) biaxial
- (3) triaxial
- nonaxial
- Each type is based on the number of axes of movement that exist at the joint. Axial motion or rotary motion is seen in the uniaxial, biaxial and triaxial classification. The nonaxial classification refers to motion of a body part that does not occur around an axis but is described as linear.
Uniaxial Joints
allows movement in one plane and around one axis. Referred to as one degree of freedom.
Hinge Joints
These uniaxial joints allow movement in only one plane such as flexion and extension. Example: elbow (humeroulnar joint), PIP and DIP joints of the hands and feet, and IP joints of the thumb and big toe.
Pivot Joints
these joints allow movement in one plane such as neck rotation (C1 (atlas) with C2 (axis) vertebra – atlantoaxial joint) and pronation and supination (forearm or radioulnar joint) - this occurs at the proximal end of the radius and ulna.
Biaxial Joint
allows movement in two planes and around two axes. Referred to as two degrees of freedom.
Ellipsoid /Condyloid
These biaxial joints consist of a reduced ball and socket joint which allows movement in two planes such as adduction/abduction and flexion/extension. Whenever movement occurs in two planes circumduction will also be present. Example: MCP (also called MP) joints of digits 2, 3, 4, and 5 of the hands and feet, the temporomandibular joint (TMJ), wrist (radiocarpal joint), knee (tibiofemoral joint) and ankle joint.
Saddle
This biaxial joint allows movement in two planes such as flexion / extension, adduction / abduction and therefore circumduction. Example: CMC (carpometacarpal) joint of the thumb.
Multiaxial/Triaxial
allows movement in three planes and around three axes. Referred to as three degrees of freedom.
Ball and Socket
These joints allow movement in three planes such as flexion / extension, adduction / abduction and therefore circumduction as well as internal / external rotation. Example: Shoulder (glenohumeral) joint and Hip (coxofemoral) joint.
Nonaxial
motion of a body part that does not occur 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 or glides the same amount as 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. These nonaxial joints are referred to as Planar or Gliding Joints. Example: intercarpal and intertarsal joints, scapulothoracic joint (ST) and the acromioclavicular joint (AC).
Ligament
joins bone to bone. Ligaments are tough and non-elastic functioning to hold bones together. They function to prevent dislocation and to limit motion in undesirable directions. Example: when the knee is in extension it cannot move side to side unless there is injury to the ligaments that prevent this movement. Therefore ligaments are found in the planes in which the joint requires stability.
Loose-packed position
position where surfaces are not in as much contact, some part of the ligaments are slackened. (knee flexion)
Closed-packed
position of maximum contact between articular surfaces; ligament are maximally taunt. (knee extension)
Tendons
connective tissue that connects the muscle to the bone. Located on the ends of muscles.
Muscles
allows the body to move and the contractions produce heat which helps to maintain a constant body temperature.
Joint Stability
With an increase in the number of stabilizing factors (ligaments) comes a decrease in mobility. When the number of stabilizing forces decreases there comes an increase in mobility and a proneness to injury. Example: The hip has greater stability and therefore less mobility and less proneness to trauma. The shoulder is less stable and has greater mobility and therefore greater proneness to injury.
