Joints

Anatomy & Pathology

Joints

A union or junction between two or more bones. Articulation

Joint Classification

Joints can be classified by several criteria-

Simple or Compound- by the number of bones articulating with each other. Simple- articulations united by two

bones. Compound- articulations united by

more than two bones.

Joint Classification

Structural Classification- classified by their uniting medium. Fibrous- an articulation united by fibrous

tissue allowing little or no movement. Cartilagenous- an articulation united by

fibrocartilage, hyline cartilage, or both as in a symphysis.

Synovial- an articulation united by a synovial joint capsule, these joints are freely movable.

Joint Classification Functional Classification- indicates

the degree of motion possible. Synarthrosis- the tight, fixed union

allowing little or no movement and having great strength. Ex. Skull bones

Amphiarthrosis- connected by CT or fibrocartilage allowing slight motion. Ex. Vertebrae

Diarthrosis- united by a joint capsule and are freely moveable- synovial joints.

Gomphosis- the name for fibrous implantation of teeth into the jaw.

Synovial Joints Characterized by their

mobility, joint cavity, articular cartilage, synovial membrane, and fibrous capsule.

This is the most common type of joint.

Functionally, it is freely moveable.

Synovial Joints

Joint capsule- the 2 layered structure surrounding the joint.

Fibrous layer- the white & yellow elastic fibrous part of the joint capsule. It attaches to the periosteum on or near the

margin of the articular cartilage. Synovial membrane- the inner lining

of the fibrous layer. It is highly vascular, nerve rich, and

produces synovial fluid.

Synovial Joints

Synovial fluid- the viscous liquid that lubricates the joint and supplies nutrients.

Articular cartilage- the translucent cartilage covering the ends of bones. It reduces the effects of friction.

Ligaments- strong bands of white fibrous CT uniting bones. They function to keep joint surfaces in

apposition and still allow movement.

Synovial Joints

Meniscus or Disc- a plate of fibrocartilage partially or completely dividing a joint cavity. It functions to allow a greater variety

of motion and alleviate friction. Bursa- a sac-like structure between

different tissue that reduces friction between these tissues.

Classification of Synovial Joints By movement- the contraction of

muscles crossing a joint and the shape of a joint produce its characteristic movements. Plane- arthroidal joint having flat

articular surfaces allowing a gliding or sliding motion.

Ball & Socket- a spheroidal joint consisting of a spheroidal head fitting into a pit or socket.

Classification of Synovial Joints By movement…

Hinge- a joint allowing movement at right angles.

Pivot- allows rotation around a longitudinal axis of a bone.

Condylar- formed by 2 condyles of one bone fitting into the cavities of another bone.

Movement of Synovial Joints

Flexion- decreasing the angle between 2 bones. Extension- increasing the angle between 2 bones. Abduction- moving a part away from the medial

plane. Adduction- moving a part toward the medial plane. Circumdunction- movement circumscribing a cone

shape accomplished by combining flexion, abduction, extension, & adduction.

Rotation- movement around the long axis of a part. Universal- all of the above movements.

Shoulder Joint

Humeroradioulnar

Humeroradioulnar Head of the radius-

articulates with the hureral condyle & the ulna.

Trochlear notch of the Ulna- articulates with the trochlea of the humeral condyle.

Anconeal process of the Ulna- fits into the olecranon fossa of the humerus.

Humeroradioulnar

Carpal Joints

A hinge joint allowing flexion and extension with some lateral movement.

It consists of 3 main joints: antebrachiocarpal, middle carpal, & carpometacarpal.

Antebrachiocarpal

Radiocarpal joint Between the

distal radius & ulna and the proximal row of carpal bones.

Lots of movement.

Middle Carpal Joint

Between the 2 rows of carpal bones.

It communicates with the carpometacarpal joint.

Lots of movement.

Carpometacarpal Joint

Between the distal row of carpal bones and the metacarpal bones.

Very little movement.

Intercarpal Joints

Plane joints between the individual carpal bones.

Articulations between the proximal ends of the metacarpal bones.

Metacarpaophalangeal Joints

The articulation between the metacarpals & the proximal phalanges including the palmar sesamoid bones.

A modified hinge joint allowing flexion & extension.

Phalangeal Joints Proximal

Interphalangeal joints- synovial joints between the proximal and middle phalanges.

Distal Interphalangeal Joints- between the middle and distal phalanges.

Pelvic Joints

relatively immovable articulation between the wings of the sacrum & the ilium. This is a combined

cartilagenous and synovial joint.

Pelvic Joints Pelvic

Symphysis- a slightly moveable joint between the 2 hip bones.

Coxofemoral- the ball & socket type synovial joint between the head of the femur and the acetabulum of the pelvis.

Stifle

A condylar joint which acts like a hinge joint with a little rotation.

Stifle

**Patellar Ligament- the part of the tendon insertion of the quadriceps muscle between the patella and tibial tuberosity.

Stifle

Medial & Lateral Menisci- the crescent, fibrocartilagenous discs between the tibial & femoral articulating condyles.

Stifle

Cranial & Caudal Cruciate Ligaments- intra-articular ligaments named for their tibial attachments. **Cranial CL- inserts

cranially on the tibia. **Caudal CL- inserts

caudally on the tibia.

Tibiofibular Joint

Tarsus

“Hock” A compound

hinge joint allowing for flexion & extension.

Skull Joints

Mandibular Symphysis- cartilagenous joint joining the left & right mandibular bodies.

Vertebral Column

Intervertebral articulations consist of 2 types of joints: Cartilagenous- are formed by

interveterbral disks joining adjacent vertebral bodies.

Synovial- are formed by caudal and cranial articular processes of adjacent vertebrae.

Vertebral Column

Costovertebral Joints- the 2 distinct articulations between most ribs and the vertebral column. The head of each rib forms a ball &

socket joint with the vertebrae. The tubercle of each rib forms a joint

with the transverse process of the vertebrae.

Each has a joint capsule.

Vertebral Column

Atlanto-occipital Joint- the “yes” joint.

Atlanto-axial Joint- the “no” joint. A pivot joint between the axis &

atlas. Intervertebral Disks-

The layers of fibrocartilage between bodies of adjacent vertebrae each consisting of an outer fibrous ring and an inner pulpy nucleus.

Vertebral Column

Costochondral Junction or Joints- the fibrous joints between the ribs and costal cartilages.

Joint Pathology

Osteochondrosis Dessicans

A failure of cartilage maturation.

Pressure on such defective cartilage may cause a piece (joint mouse) to be separated and float free in the synovial space.

Pathology…

Arthritis- Inflammation of a joint

Bursa- Small, fluid-filled sac in places where

friction might occur Bursitis-

Inflammation of the bursa

Pathology…

False Joints- a joint formed in an unreduced (unhealed) fracture, having all the structures of a synovial joint.

Luxation or Dislocation- an articular separation usually due to injury or degenerative changes.

Hip Dysplasia

A malformed hip joint resulting in a progressive degenerative disease having a high incidence in some breeds.

Hip Dysplasia

Cranial Cruciate Ligament Rupture and Repair When the cruciate ligament

is torn or stretched, instead of moving like a hinge, the knee joint will actually make a sliding motion.

This abnormal motion and instability creates trauma within the joint that leads to wearing of cartilage, increased synovial fluid production and inflammation.

CCLR

A torn cruciate ligament can occur in any dog if just the right (or wrong!) forces impact the knee joint.

Most commonly seen in larger breeds of dogs and in dogs that are overweight

The ACL surgical procedure does not actually repair the torn ligament but rather replaces the ligament with artificial material that takes over the function of the Cruciate Ligament.

Cranial Drawer Test

Patellar Luxation Patellar luxation is usually a congenital

condition in which the kneecap, or patella, dislocates outside of its normal trochlear groove.

Dislocation, clinically referred to as luxation, can occur on either the medial, or inside surface, or the lateral, or outside surface, of the knee.

There are varying degrees of patellar luxation that are graded depending on whether the patella is intermittently or constantly luxated.

This abnormal displacement of the kneecap results in pain, cartilage damage, and arthritis.

There are varying degrees of severity of this disease, and surgery may be needed.

Joint Fluid Analysis

Indications

Helps determine the cause of pain or swelling in a joint

Synovial fluid is collected for cytological, bacterial or biochemical analysis

Normal synovial fluid has a low cellularity, with virtually no red blood cells & only small numbers of leukocytes.

The main functions of synovial fluid are nutritive support, lubrication, and “cushioning” of the articular cartilage.

In addition to cytologic evaluation, the fluid should be assessed for: Volume obtained Turbidity Mucin quality/concentration Protein concentration Color Viscosity

Sample Handling & Test Priorities

Normal synovial fluid does not clot. However, with hemorrhage or blood

contamination, samples may clot unless processed immediately or placed in an anticoagulant tube.

EDTA is preferred for cytologic examination, while heparin is recommended for the mucin clot test.

Color & Turbidity

Normal synovial fluid is clear to straw yellow and non-turbid. Turbidity, when present, is caused by

cells, protein (or fibrin), or cartilage.

Viscosity

Viscosity is frequently decreased in joints with bacterial inflammation.

Synovial Fluid

Synovial Fluid

The End!!