CHAPTER 7:
JOINTS
A. INTRODUCTION
1. A JOINT OR ARTICULATION, is a point of contact between bones, between cartilage
and bone, or between teeth and bones.
2. The structure of the joint determines how it will function.
3. The ranges of movements of a joint are IMMOVABLE, SLIGHTLY IMMOVABLE, or
FREELY MOVABLE.
4. Articulations are supported by ligaments and joint capsules, as well as by the
attachment of surrounding muscles.
B. CLASSIFICATION OF JOINTS
1. The STRUCTURAL CLASSIFICATION of joints includes fibrous, cartilaginous, and
synovial.
2. The FUNCTIONAL CLASSIFICATION of joints defines the DEGREE OF MOVEABILITY of the
joint and includes SYNARTHROSES (immovable joints), AMPHIARTHROSES (slightly
movable joints), and DIARTHROSES (freely movable joints).
C. FIBROUS JOINTS
1. The three types of fibrous joints are SUTURES, SYNDESMOSES, and GOMPHOSES. They
are held closely together by fibrous connective tissue and provide little or no
movement.
2. SUTURES are found between the bones of the skull and are immovable. Functionally,
they are classified as synarthrotic joints. Examples of sutures are the coronal suture,
lambdoidal suture, and parietal suture.
3. SYNDESMOSES contain large amounts of fibrous connective tissue between the bones.
They are slightly movable and are functionally classified as amphiarthrotic joints. An
example of a syndesmosis is the distal articulation of the tibia and the fibula.
4. A GOMPHOSIS is a type of fibrous joint in which a cone-shaped peg fits into a socket
such as the articulations between the teeth and the bones of the mandible and the
maxilla. Gomphoses are always synarthrotic.
D. CARTILAGINOUS JOINTS
1.
are held together by cartilage and afford little or no
The two types of cartilaginous joints are SYNCHONDROSES and
CARTILAGINOUS JOINTS
movement.
SYMPHYSES.
2. A SYNCHONDROSIS is a joint in which the binding material is hyaline cartilage.
Synchondroses are functionally classified as synarthroses.
Examples of
synchondroses include the epiphyseal plate and the articulation of the first rib and the
sternum.
3. A SYMPHYSIS is joined by a broad, flat, fibrocartilagenous disc. It affords slight
movement and is classified functionally as an amphiarthrotic joint. Examples of a
symphysis are the intervertebral discs and the symphysis pubis.
E. SYNOVIAL JOINTS
1. The typical DIARTHROTIC JOINT contains a SYNOVIAL CAVITY lined with a SYNOVIAL
MEMBRANE, an ARTICULAR CARTILAGE, and an ARTICULAR CAPSULE. Most synovial
joints contain accessory ligaments, articular discs and bursae.
2. The ARTICULAR CAPSULE consists of an outer fibrous capsule and an inner synovial
membrane. It encloses the synovial cavity and unites the articulating bones.
3. The SYNOVIAL MEMBRANE secretes synovial fluid, which lubricates the joints and
provides nourishment for the articular cartilage.
4. Inside some synovial joints, such as the knee, are pads of fibrocartilage called
ARTICULAR DISCS OR MENISCI.
5. BURSAE are sac-like structures, which are situated between bones and several other
structures such as skin, tendons, ligaments, and muscles. Their function is to reduce
friction between the moving parts.
6. The presence of a JOINT CAVITY permits movement. This movement is limited due to
the shape of the articulating bones, tension of the ligaments and apposition of soft
parts.
F. TYPES OF SYNOVIAL JOINTS
1. Synovial joints are divided into six subtypes. These are PLANAR, HINGE, PIVOT,
CONDYLOID, SADDLE, and BALL-AND-SOCKET.
2. PLANAR joints contain an articular surface which is flat and allows a gliding
movement. Examples are the joints between the carpals, tarsals, sternum and
clavicle, and scapula and clavicle.
3. HINGE JOINTS allow one bone to move into the concave surface of another bone.
These joints allow for flexion and extension and are exemplified by the elbow and
knee joints.
4. PIVOT JOINTS contain a round or pointed surface of one bone which articulates within
a ring formed by another bone. This allows for ROTATION and can be exemplified by
the atlanto-axial joint.
5. CONDYLOID JOINTS contain oval-shaped bones which fit into a depression in another
bone. This allows for ABDUCTION and ADDUCTION as well as CIRCUMDUCTION.
6. SADDLE JOINTS are joints in which are one bone is shaped like a saddle and the other
bone is shaped like a rider Saddle joints permit side to side and up-down movements.
This can be seen in the trapezium of the carpus and the metacarpal of the thumb.
7. BALL & SOCKET JOINTS contain one bone with a ball surface and another with a cuplike depression. These joints allow for ABDUCTION and ADDUCTION, ROTATION and
CIRCUMDUCTION, FLEXION and EXTENSION. They can been illustrated by the hip and
shoulder joints.
G. TYPES OF MOVEMENT AT SYNOVIAL JOINTS
1. The major movements that occur at synovial joints are the following:
 FLEXION—decrease in the angle between bones
 EXTENSION—increase in the angle between bones
 ABDUCTION—movement of a bone away from the midline
 ADDUCTION—movement of a bone toward the midline
 CIRCUMDUCTION—movement of the distal end of a part of the body in a circle
2. ROTATION – a bone revolves around its own longitudinal axis.
3. Specialized movements that occur at synovial joints include the following:
 ELEVATION—upward movement of a body part
 DEPRESSION—downward movement of a body part
 PROTRACTION—movement of the mandible or shoulder forward
 RETRACTION—movement of the mandible or shoulder backward
 INVERSION—movement of the sole medially
 EVERSION—movement of the sole laterally
 DORSIFLEXION—movement of the foot in the direction of the dorsum
 PLANTARFLEXION—movement of the foot in the direction of the plantar surface
 SUPINATION—forearm movement so that the palms are forward or upward
 PRONATION—forearm movement so that the palms are backward or downward
H. KNEE JOINT
1. The knee joint represents the most complex of the synovial joints, and
contains many structural features.
2. The main structures of the knee are as follows:
 ARTICULAR CAPSULE
 PATELLAR LIGAMENT
 OBLIQUE POPLITEAL LIGAMENT
 ARCUATE POPLITEAL LIGAMENT
 TIBIAL COLLATERAL LIGAMENT
 FIBULAR COLLATERAL LIGAMENT
 ANTERIOR CRUCIATE LIGAMENT
 POSTERIOR CRUCIATE LIGAMENT
 MEDIAL MENISCUS
 LATERAL MENISCUS
 BURSAE
I. COMMON DISORDERS
1. RHEUMATISM refers to any painful state of supporting structures of the body such as
bones, ligaments, tendons,
joints, and muscles.
2. ARTHRITIS refers to several disorders characterized by inflammation of joints
accompanied by stiffness.
3. RHEUMATOID ARTHRITIS (RA) is an autoimmune disease and is characterized by an
inflammation of the synovial membranes.
4. OSTEOARTHRITIS is a degenerative joint disease characterized by deterioration of the
articular cartilage. It is non-inflammatory and generally affects the weight-bearing
joints.
5. GOUTY ARTHRITIS is a condition in which sodium ureate crystals are deposited in the
soft tissues of joints, causing inflammation, swelling, and pain.
6. A SPRAIN is a forcible wrenching or twisting of a joint that stretches or tears its
ligaments without dislocation.
7. A STRAIN is a stretched or partially torn muscle.