Kinesiology Chapter 4: Articular System and Arthrokinematics
Pima Medical Institute OTA 125: Kinesiology Chapter 4: Articular System and Arthrokinematics
I. Function of Joints
Joints are the articulation between bones.
Important functions of joints include:
Allowing motion.
Providing stability.
These functions can be contradictory and are determined by the shape and structures of the joint.
II. Classification of Joints
Joints can be classified based on two criteria:
Type:
Two types of joints exist:
Synarthrosis:
Primarily provides stability.
Diarthrosis:
Primarily allows mobility.
Number of axes of motion:
Stability or mobility based on the number of axes present in the joint.
III. Synarthrosis
Synarthrodial
There are three types of synarthrodial joints:
Fibrous joints:
Function primarily to provide stability.
Characterized by a thin layer of fibrous periosteum that exists between articulating bones.
Bones are shaped to interlock, as seen in the skull sutures.
Ligaments or interosseous membranes are found between bones.
Interosseous membrane examples include:
Between tibia and fibula.
Between radius and ulna.
Ligament example:
Distal tibiofibular joint.
Gomphosis:
The arrangement can be described as peg-in-socket, specifically related to teeth.
Cartilaginous joints:
Allow for small amounts of bending, twisting, and compression.
Bones are joined by either hyaline or fibrocartilage.
Example: Intervertebral disks comprise fibrocartilage.
IV. Diarthrodial Joints (Synovial Joints)
Diarthrodial joints typically provide greater mobility and are characterized by:
No direct union between bone ends.
Presence of a joint space.
Surrounding joint capsule.
Synovial membrane.
Synovial fluid.
Articular cartilage.
Supporting ligaments.
V. Number of Axes (Degrees of Freedom)
The degrees of freedom vary based on the type of joint:
Non-axial joint:
Allows slight gliding motion.
Uniaxial joint:
Moves in one plane about one axis.
One degree of freedom, examples include:
Hinge joint.
Pivot joint.
Biaxial joint:
Moves in two planes about two axes.
Two degrees of freedom.
Example: Carpometacarpal (CMC) joint of the thumb, classified as a sellar or saddle joint.
Triaxial joint:
Moves in three planes about three axes.
Three degrees of freedom.
VI. Structures of a Joint
Joints primarily consist of:
Bones: Form the rigid structure of the joint.
Ligaments:
Composed of fibrous connective tissue, providing support and joining bones.
Nonelastic, includes both capsular and intracapsular ligaments.
Capsule:
Surrounds and encases the joint.
Composed of an outer fibrous layer, adding stability and protection to the joint.
Synovial membrane:
Inner layer of the capsule, characterized by thick vascular connective tissue.
Produces synovial fluid, which consists of water and dissolved proteins.
Functions of synovial fluid:
Lubricates articular cartilage.
Provides nutrients to the joint structures.
Acts as a shock absorber.
Bursa:
Fluid-filled sacs that provide cushioning and reduce friction.
VII. Cartilage
Cartilage is dense fibrous connective tissue that withstands pressure and tension.
There are three types of cartilage:
Hyaline cartilage:
Found at ends of bones of synovial joints.
Provides a smooth surface for articulation.
Lacks blood and nerve supply, thus has limited repair capabilities.
Fibrocartilage:
Present in both synovial and cartilaginous joints.
Functions primarily in shock absorption.
Examples include:
Menisci of the knee—alter the shape of joint surfaces.
Labrum—deepens a joint cavity.
Disks:
Intervertebral disks.
Fill gaps between bones, such as between ulna and carpal bones.
Elastic cartilage:
Maintains a structure’s shape while allowing flexibility.
Examples include:
External ear
Larynx
VIII. Tendons
Tendons connect muscles to bone.
Tendons have various shapes, including cylindrical cords or flat bands.
Tendons may be encased in a tendon sheath, which is a sleeve-like structure surrounding the tendon to reduce friction.
Aponeurosis:
Broad, flat, tendinous sheet of connective tissue.
Examples include:
Thoracolumbar fascia: Attachment site for latissimus dorsi.
Linea alba: Midline structure of the abdominal wall.
IX. End Feel
Describes the sensation perceived when passively moving a patient’s joint to the end of its range of motion (ROM).
Used to determine the reason for limitations in further motion at the joint.
Normal end feel:
What is expected at the end of a normal ROM.
Abnormal end feel:
Occurs when the end of ROM is not normal.
May indicate pain, swelling, muscle guarding, or changes in anatomy.
Different types of end feel include:
Soft end feel:
Characterized by compression of soft tissue (muscle bulk) halting motion.
Example: Soft "give" at the end of ROM.
Firm end feel:
Resulting from tension in structures (ligaments, capsules, muscles) limiting motion.
Example: Slight "give" at the end of ROM.
Hard end feel (Bony end feel):
Characterized by hard or abrupt limitation of motion.
Example: No "give"—bone on bone.
Empty end feel:
Indicates an abrupt halt to motion typically due to pain.
Boggy end feel:
Soft or spongy end feel, usually signifies swelling.
Muscle spasm:
Reflexive guarding or abnormal muscle tone, often due to an acute injury.
Springy block:
Indicative of internal derangement of a joint, such as torn cartilage.
X. Joint Surfaces
The shape of joint surfaces determines arthrokinematic motions.
Types of joint surfaces include:
Ovoid:
Characterized by a concave-convex relationship.
One bone often larger than the other.
Sellar (Saddle):
Each surface exhibits both concave and convex surfaces.
Example: Carpometacarpal (CMC) joint of the thumb.
Flat:
Limited motion, typically occurs between carpal or tarsal bones.
XI. Joint Surface Congruency
Refers to the degree to which joint surfaces fit together or match.
A joint may be congruent in one position and incongruent in all other positions.
Close-packed (Closed-pack) position:
Most congruent position of a joint.
Involves slight compression of the joint, enhancing stability.
This position is used to test capsule and ligament integrity of the joint.
Open-packed (Loose-packed) position:
Displays less or minimal congruency of joint surfaces.
Associated with laxity of joint capsule and ligaments, permitting greater mobility of the joint.
XII. Types of Arthrokinematic Motions
All joint osteokinematic motion includes at least one type of arthrokinematic motion.
Arthrokinematic motions are characterized by type and direction of movement in relation to the anatomical position.
The three types of arthrokinematic motions include:
Roll:
Describes the motion of one surface rolling on an adjacent surface.
A new point on one joint surface contacts a new point on the adjacent joint surface continuously during motion.
Glide (Slide):
Describes a linear movement of one joint surface parallel to the plane of an adjacent joint surface.
A single point of one joint surface contacts new points on the adjacent joint surface during the motion.
Spin:
Involves rotation of a single point on one joint surface about a single point on the adjacent joint surface.
The same point on each joint surface remains in contact throughout the motion.
XIII. Concave-Convex Rule
This rule describes the direction of arthrokinematic motion during osteokinematic movements.
A concave joint surface will glide on a fixed convex surface in the same direction as the end of the moving bone that is farthest from the joint at which motion is occurring.
Conversely, a convex joint surface will glide on a fixed concave surface in the opposite direction as the end of the moving bone that is farthest from the joint at which motion is occurring.
XIV. Kinetic Chain and Concave-Convex Rule
To determine the direction of arthrokinematic motion, consider the following factors:
Which joint surface is in motion?
Is the joint surface of the moving limb segment concave or convex?
Is the limb segment in an open or closed kinetic chain configuration?
XV. Common Joint Pathologies
Types of joint pathologies include:
Dislocation: Complete separation of joint surfaces.
Subluxation: Partial dislocation of a joint.
Osteoarthritis: Wear and tear arthritis affecting joint surfaces.
Sprains: Tears in ligaments safeguarding joints.
Strains: Overstretching of muscles.
Inflammation: A normal response to injury, which includes:
Tendonitis: Inflammation of a tendon.
Tenosynovitis: Inflammation of the sheath surrounding a tendon.
Bursitis: Inflammation of one or more bursae.
Capsulitis: Inflammation of the joint capsule.
XVI. Capsular Pattern
Describes a characteristic pattern of motion loss when capsular tightness is present.
It identifies the course of motion restriction and directs patient management.