Joints

Chapter 8, Section 1

The science of joints is called arthrology.

Joints, also called articulations, are functional junctions between two bones

Functions of joints1. Bind skeleton together2. Enable body movements3. Makes growth possible4. Permit changes in skeleton for childbirth

Classification of Joints

Classifications based on amount of movement1. Synarthrotic = immovable

2. Amphiarthrotic = slightly moveable

3. Diarthrotic = fully movable

Classifications by types of tissue:1. Fibrous joint = dense connective tissue

2. Cartilaginous joint = bones connected by cartilage

3. Synovial joint = contains a synovial membrane

Fibrous Joints

There are three (3) types of fibrous joints:• Syndesmosis• Suture• Gomphosis

1. Syndesmosis:Bones are connected by a sheet or bundle of fibrous tissue.

Examples include the interosseous membrane and interosseous ligaments between the tibia and fibula.

Interosseous membrane between tibia and fibula is a syndesmosis joint.

2. Suture:• Thin layer of dense

connective tissue

• Connects flat bones of the skull (sutural ligaments)

• Synarthrotic

Fibrous Joints

3. Gomphosis:• Cone-shaped bony process

in a bony socket

• Example includes a tooth anchored into a bony socket

Cartilaginous Joints

• There are two (2) types of cartilaginous joints:• Synchondrosis• Symphysis

1. Synchondrosis• Bones are united by a band of

hyaline cartilage.

• Located between manubrium of sternum & 1st rib

• Also located at epiphyseal plates of developing bone

• Movement is synarthrotic

2. Symphysis• A pad of fibrocartilage

between two bones

• Examples include the pubic symphysis and intervertebral discs

• Movement is amphiarthrotic.

Cartilaginous Joints

General Structure of Synovial Joints

Synovial Joints are Freely movable (Diarthrotic)

Structures include:• Articular cartilage

• Synovial membrane – secretes synovial fluid

• Joint cavity – filled with synovial fluid

• Joint capsule – dense connective tissue that stabilizes and protects joint

Figure 8.7 The generalized structure of a synovial joint.

General Structure of Synovial Joints

Structures include:• Ligaments – bundles of

collagenous fibers that reinforce the joint capsule

• Menisci (sing. Meniscus) – pad of fibrocartilage that separates some joints.

• Bursa – sac filled with synovial fluid. • Bursitis = inflammation

of bursa

Figure 8.8 Menisci separate the articulating surfaces of the femur and tibia. Several bursae are associated with the knee joint.

Types of Synovial Joints

1. Ball-and-socket • rounded head + cup-shaped socket.• Movement in all planes (multi-axial).• Allows for rotation• Includes hip joint and shoulder joint.

2. Condylar joint• Oval condyle + elliptical socket• Movements in most planes (bi-axial)• No rotational movement• Joints between metacarpals and

phalanges/

3. Plane (Gliding) Joint• Flattened bones slide across each

other• Includes carpals and tarsals• ribs 2-7 articulate with sternum

Types of Synovial Joints

4. Hinge joint• Increases or decreases angel

between bones• Includes elbow joint• Joints between phalanges

5. Pivot Joint• Rotation around a central axis

(uni-axial)• Joint between radius and ulna• Joint between atlas (C1) and

axis (C2).

Types of Synovial Joints

6. Saddle Joint• 2 concave bones positioned at

right angles• Includes metacarpal and carpal

of thumb

End of Chapter 8, Section 1

Types of Joint Movements

Section 2, Chapter 8

Movement at a joint occurs when a muscle contracts and its fibers pull its moveable end (insertion) towards its fixed end (origin).

Types of Joint Movements

Abduction = movement away from the midline(think of someone being abducted, or taken away)

Adduction = movement towards the midline (think of adding together)

Flexion = decreases the angle of a joint• Bend elbow

Extension = increases the angle of a joint• Extend elbow

Hyperextension = extension beyond the anatomical position

• bend hand back, bend head back beyond anatomical position

Types of Joint Movements

Rotation = movement around a central axis• Twisting the head from side to side

Circumduction = movement so end follows a circular path

• moving the finger in a circular motion without moving the hand.

Types of Joint Movements

Elevation = raising a part• Shrugging the shoulders

Depression = lowering a part• Drooping the shoulders

Types of Joint Movements

Protraction = moving a part forward• thrusting head forward

Retraction = moving a part backward• pulling the head backward

Supination = turning the hand so the palm faces upward or anteriorly

Pronation = turning the hand so the palm faces downward or posteriorly

Types of Joint Movements

Dorsiflexion = movement at the ankles that points toes towards the sky

Plantar flexion = movement at the ankles that points toes towards the ground

Example: turning a doorknob clockwise with your right hand.

Eversion = turning the foot so the planter surface faces laterally

Inversion = turning the foot so the plantar surface faces medially

Types of Joint Movements

End of Chapter 8, Section 2

The Knee Joint and Joint Disorders

Chapter 8, Section 3

Knee JointThe knee joint is the largest and most complex synovial joint in body.

Two distal condyles of the femur articulate with two proximal condyles of the tibia. This is a condylar joint.

The femur also articulates anteriorly with the patella. This is a plane joint.

Figure 8.21 Figure 8.20

1. Synovial Membrane• Secretes synovial fluid

2. Joint Cavity • Stores synovial fluid

3. Joint Capsule• Relatively thin support• Reinforced by several

ligaments and tendons

Knee Joint

General structures of a synovial joint in the knee

Figure 8.20

1. Patellar tendon - The patella is partially enclosed in tendons fused together from the thigh muscle.

2. Patellar ligament – continuation of patellar tendon. Extends from patella to the tibial tuberosity.

Knee Joint

Several ligaments and tendons strengthen the knee joint.

Knee Joint

Figure 8.21a Anterior right knee with patella removed.

3. Tibial collateral ligament – connects medial condyle of femur with medial condyle of tibia.

4. Fibular collateral ligament – connects lateral condyle of femur with head of fibula.

5. Anterior & Posterior Cruciate ligaments – provide additional support to medial surface of tibia and femur

Ligaments continued:

Knee Joint

Two menisci (medial & lateral meniscus) separate the femur and tibia, and align them.

Figure 8.20 (a) sagittal section of the knee joint. (b) Photograph of the left knee joint (frontal

section)

Three major bursae surround the knee joint.

Knee Joint

1. Suprapatellar bursa• Largest bursa in body

2. Prepatellar bursa• Between patella and skin• Housemaid’s knee =

prepatellar bursitis

3. Infrapatellar bursa

Figure 8.20a

Joint Disorders

Sprain = overstretching or tearing of connective tissue (tendons, ligaments, or cartilage) associated with a joint.

However, the bones are not disarticulated.

Joint Disorders

Arthritis = inflamed, swollen, and painful joints.

1. Osteoarthritis• Most common arthritis

• Occurs with aging

• Articular cartilage degenerates, causing bone to rub against bone.

• Results in stiff and painful joints

• Fingers may appear gnarled and knee may bulge.

Osteoarthritic fingers often take

on a gnarled appearance.

2. Rheumatoid Arthritis• Autoimmune disorder (immune

system attacks tissue)

• Synovial membrane thickens & becomes inflamed

• Mass of fibrous connective tissue (Pannus) invades synovial space.

• Fibrous pannus destroys articular cartilage, and the joints may swell and ossify.

Knuckles may swell as a result of rheumatoid arthritis.

End of Chapter 8, Section 3

Other symptoms of Rheumatoid Arthritis:• low-grade fever, fatigue, appetite, stiffness.

Joint Disorders