Chapter 8- Joints Flashcards
Joints (articulations)
the site where 2 bones meet
The shape of a joint determines
how much movement it allows
General functions of joints (2)
- Mobility- allow movement of various body parts
2. Stability- hold the skeleton together
Joints allow small amounts of movement are
More stable. They are less likely to dislocate and damage internal organs
In general, how are joints classified?
By structure and function
What is the structural joint classification defined by?
The type of tissue that connects bones at the articulating surface
Structural joint classifications (3)
- Fibrous
- Cartilaginous
- Synovial
Joint cavity
Only found in synovial joints. It is defined as a very small empty space between the bones that form the joint or around the joint itself. Contains synovial fluid
What is the functional joint classification defined by?
The amount of movement allowed by the joint
Functional joint classifications (3)
- Synarthroses
- Amphiarthroses
- Diarthroses
The axial skeleton typically contains which functional joint categories?
Synarthroses and amphiarthroses are prevalent in the axial skeleton.
Synarthroses are held very tightly together. We don’t want most of the bones in the axial skeleton (ribs, etc.) to move around
The appendicular skeleton typically contains which functional joint categories?
Diarthroses are prevalent in the appendicular skeleton
We want the limbs to be able to move around and want the dexterity in fingers for certain tasks
Fibrous joints
Joints composed of collagen fibers of connective tissue, contain no joint cavity. Fibrous joints have short collagen fibers, prevents movement
Fibrous joints typically include which functional joint classifications?
Mostly synarthroses, some amphiarthroses
Types of fibrous joints (3)
- Sutures
- Syndesmoses
- Gomphoses
Sutures
“Seams”- joints found only between the bones of the skull. Composed of bundles of extremely strong and short collagen fibers
The fibers are clumped/bundled together, making them strong and allowing VERY little movement
Fontanelles
Soft spots of a fetus or infant- this allows skull flexibility during birth. These areas are not ossified and the sutures of the skull are not completely formed. Large chunks of fibrous tissue separate the bone- fibrous tissue is strong and will not tear away easily
By what age will fontanelles be ossified?
18 months
Why are fontanelles important?
In fetuses, the brain grows very quickly- fontanelles allow the brain to grow without being locked in place
They also allow the infant’s head to squeeze through the pelvic bone without damage
Syntoses
What sutures form if they ossify- syntoses are not considered joints. Formation is normal, but it doesn’t happen to everyone and usually happens later in life
Syndemoses
Bones are connected to one another only by ligaments. Movement depends on the length of the ligaments. The longer the fiber, the more movement allowed.
Ligaments
bands of fibrous tissue that join bone to bone
How does the ligament between the distal portions of the tibia and fibula influence their movement?
The interosseous ligaments between the tibia and fibula in the lower leg allow them to move relative to each other but not that much- influences the amount of movement in the foot- we can kind of move the foot but can’t flip it all the way around. Short ligament= limited movement
How does the ligament between the radius and ulna influence their movement?
The ligament between the radius and ulna has longer fibers and therefore you can move the hand much more. The bones form an x when the hand is facing downward and are parallel when hand is facing up
Gomphoses
The only joint type that does not join bone to another bone- joins the teeth to the bony alveolar sockets. Fibers are very short, providing limited movement- don’t want the teeth moving too much or coming out
Periodontal ligament
joins the bone of the mandible/maxilla to the centrum of the tooth
How do braces work?
Braces force movement of the periodontal ligament/joint. The periodontal ligament does not want to move, which is why braces are painful.
Retainers are necessary so the periodontal ligament can’t force the teeth back to normal
Cartilaginous joints
bones joined by cartilage, no joint cavity
Cartilaginous joints typically include which functional joint classifications?
Synarthroses and amphiarthroses
Benefit- prevents excessive moment
Types of cartilaginous joints (2)
- Synchondroses
2. Sympheses
Synchondroses
bones united with a plate of hyaline cartilage. Example- epiphyseal plate in long bones, costal cartilage
Which functional classification of joints are typically found in synchondroses?
synarthroses
Costal cartilage
Costal cartilage joins the ribs to the sternum- don’t want the ribs shifting too much. Found at the epiphyseal plate- joins two parts of the bone. This is the only temporary joint
Symphyses
Fibrocartilage joins bone, hyaline cartilage is still found on the bone surface
Some movement is allowed, but it’s limited
Excellent shock absorber- can withstand tension and return to original shape
Ex- intervertebral joints and pubic symphysis
Intervertebral joints
Intervertebral discs are good shock absorbers (body weight, walking, running, etc) and allows for flexibility to the vertebral column without damage- this can change with age
Intervertebral disc herniation
Discs can herniate- a part of the fibrocartilaginous joint pops out of the side of the vertebrae. Can press on a muscle (impairs function and causes some pain) or a nerve (very painful). This can occur with hard blow/trauma to the back, with weight lifting if the weight is way too heavy, or with bad posture for extended periods of time, sleeping in weird position for too long
Pubic symphysis function
Pubic symphysis doesn’t allow much movement- movement occurs slightly when you shift from one leg to the other
Synovial joints
Structurally more complex than cartilaginous or fibrous joints- most joints in the body fall under this classification
Almost all located in the appendicular skeleton, they contribute to the movements of our limbs
Which functional joint classification do synovial joints usually include?
Diarthroses- they allow for substantial amount of movement compared to fibrous/cartilaginous joints
Which 6 features are found in synovial joints?
- Articular cartilage
- Joint cavity
- Articular capsule
- Synovial fluid
- Reinforcing ligaments
- Nerves and blood vessels
Articular cartilage
Hyaline cartilage covering bone ends
Function- provides cushion to prevent bone damage when weight is placed on a joint-prevents the bone ends from directly rubbing together (very painful), stores synovial fluid
Articular capsule
two layered capsule that encloses the joint cavity- forms the walls of the joint cavity. This and the articular cartilage are 2 separate structures.
Contains 2 layers
2 layers of the articular capsule
- Fibrous (outer) layer
2. Synovial membrane (inner)
Fibrous layer of the articular capsule
Outer layer that is continuous with the periosteum of bone (the diaphysis).
Function- strengthens and provides stability to joint, prevents excessive movement at the joint
Synovial membrane
Inner layer of the articular capsule. Lines any part of joint cavity except where hyaline cartilage is present
Function- produces and secretes synovial fluid
Synovial fluid
slippery fluid occupying space in joint capsule and articular cartilages. Location depends if the joint is being used (if you’re moving or not)
What happens to the synovial fluid when the joint is not active?
When the joint is not active, the fluid is viscous (like an uncooked egg white). The fluid is soaked into the articular cartilage (It is usually stored in articular cartilages).
What happens to the synovial fluid when the joint is active?
When the joint is active, fluid thins and becomes watery
Fluid is pressed out when the joint is compressed- the fluid is squeezed out into the joint cavity
What is the function of the synovial fluid?
Reduces friction between articular cartilages of articulating bones
Reinforcing ligaments
bandlike ligaments that join articulating bones. Named for location relative to the articular capsule. There are 3 types
Types of reinforcing ligaments (3)
- Capsular ligaments
- Extracapsular ligaments
- Intracapsular ligaments
Capsular ligaments
Ligaments that are a part of the outer layer of a joint capsule
Extracapsular ligaments
Ligament found outside the joint capsule
Intracapsular ligaments
Ligament found deep to the joint capsule (but not in the joint capsule)
Function of the reinforcing ligaments
Reinforce joints to provide extra stability, as these joints tend to be less stable
How are the reinforcing ligaments different in “double jointed” individuals?
Longer and looser reinforcing ligaments- allows for more flexibility in the joint. This might not be a full body thing and only happen in a specific set of joints
Innervation of the joints
Joints supplied with sensory nerve fibers (position, stretch, and pain)
Function- prevents excessive movements that could damage joints, also allows the brain to monitor posture and body movement. This prevents you from falling and causing damage/pain.
Vascularization of the joints
There is a rich blood supply to joints.
Function- capillary beds in the synovial membrane provide raw material to build synovial fluid
Bursae
Flattened sacs that contain a small amount of synovial fluid, found where ligaments, muscles, skin, tendons, and/or bone would rub together. This structure may or may not be associated with a synovial joint.
Bursae function
Reduce friction between adjacent structures
Tendon sheath
Elongated bursa that wraps completely around a tendon subjected to frequent friction, found in “crowded” tendon areas (example- tendons in the wrist and ankle).
Some joints have both (indicates a complex joint), some have one, some don’t have any. This structure may or may not be found in synovial joints
Tendon sheath function
Prevents excessive friction for a particular tendon
Tendonitis
Damage to the tendon when the tendons rub against each other
Which factors influence joint stability? (3)
- Articular surfaces
- Ligaments
- Muscle tone
How do articular surfaces influence joint stability?
The better 2 bones fit together, the more stable the joint in general.
For example, the coxal joint is more stable than the glenohumeral joint.
Why is the coxal joint relatively stable?
The acetabulum wraps almost completely around the head of the femur- very stable.
In contrast, the glenoid fossa is short and does not wrap around the head of the humerus. The head sits in the glenoid fossa like a golf ball sits on a tee- this is not very stable
How do ligaments affect the stability of a joint?
Generally, the more ligaments that surround the joint, the stronger the joint. However, if ligaments are the only supportive structure, the joint will lose stability
What do ligaments need to be most effective?
The ligaments need something to back it up to be most effective, like a reinforcing structure, or they will be overstretched. Ligaments that are overstretched will not return to their normal shape.
How does muscle tone affect joint stability?
Tendons attach muscle to bone and often wrap around/over joints. If the muscles are always slightly contracted, they pull slightly on tendons- this braces the joint
The movement allowed by synovial joints depends on
the shape of the epiphyses
Nonaxial movement
Results in gliding motion, involves flat articular surfaces on both bones
Example- plane joint in intercarpal and intertarsal joints, vertebrae
Uniaxial movement
Movement allowed in one axis only
Movement allowed- flexion, extension, rotation
Example- hinge joint between humerus and ulna and pivot joint between radius and ulna. Allows for rotation of the hand (you can supinate or pronate).
Flexion
Decreases the angle of a joint and brings the articulating bones closer together
Extension
Increases the angle between the articulating bones, typically involves straightening a flexed trunk, elbow, etc.
Rotation
The turning of a bone along its long axis. Common at the hip and is the only movement allowed between the first two cervical vertebrae. The movement can be directed toward the midline or away from it
Supination
The palm of the hand faces upward/forward, the radius and the ulna are parallel
Protonation
The palm of the hand faces downward/backward, the radius rotates over the ulna
Plane joint
A joint with flat articular surfaces, an example are intercarpal joints and vertebral articular surfaces. Usually allows nonaxial movement
Hinge joint
A joint where one articular surface is cylinder shaped and the other is trough shaped, such as the joint between the humerus and the ulna (the distal end of the humerus is cylindrical). Allows for uniaxial movement
Biaxial movement
Contains 2 axes of movement, usually at right angles to each other
Movement allowed- flexion and extension, abduction and adduction
Examples- condylar joint in knuckle, saddle joint at base of thumb
Abduction
Moving a limb away from the midline along the frontal plane
Adduction
Moving a limb toward the body midline along the frontal plane
Condylar joint
A joint where the bones have oval articulating surfaces. Example- knuckle and wrist joints (metacarpals). Allows for biaxial movement
Saddle joint
A joint where one articular surface is concave and the other is convex (curved outward). Example- carpometacarpal joints of the thumbs. Allows for biaxial movement.
Multiaxial movement
Has multiple axes of movement. Movement allowed- flexion/extension, abduction/adduction, rotation
Example- ball and socket joints of shoulder and hip
Ball and socket joint
Joint where one articular surface is cup shaped like a socket, and the other is spherical. Example- shoulder joints and hip joints. Allows for multiaxial movement
Which bones make up the temporomandibular joint?
The mandible articulates to the temporal bone
What type of joint is the temporomandibular joint?
Hinge
Temporomandibular joint
Articular disc divides the synovial cavity into superior and inferior portions. This is why you can move your jaw up and down.
Both of these movements occur during chewing. This is an evolutionary advantage in eating solid foods if you can move your jaw in a circular type of motion
This joint is most easily dislocated
What type of movements are allowed by the superior and inferior portions of the jaw?
Superior- allows lateral excursion. Sits closer to the mandibular fossa. This is why you can move your jaw left and right
Inferior- allows elevation/depression.
Glenohumeral joint
Shoulder joint- where the humerus articulates to the glenoid fossa of the scapula.
This joint is the most frequently dislocated.
Type- ball and socket joint
Most freely moving joint in the body
What 3 features is the glenohumeral joint known for?
- Reinforcing ligaments are very thin and loose
- Rotator cuff
- Glenoid labrum
Reinforcing ligaments of the glenohumeral joint
Includes the coracohumeral ligament and glenohumeral ligaments (3). They wrap around the joint to provide stability
Rotator cuff
4 muscles: subscapularis, infraspinatus, supraspinatus, and teres minor (and associated tendons) encircle the shoulder joint
What happens when the rotator cuff is damaged?
Tearing these muscles and tendons will decrease joint stability. Fixing the rotator cuff or healing it is difficult, and when it heals it won’t be the same functionally
What types of movements damage the rotator cuff?
The rotator cuff is very easily damaged by excessive/extreme movements. For example, circumduction (like pitching in baseball) puts a lot of stress on these muscles.
Glenoid labrum
Rim of fibrocartilage around glenoid fossa- provides some stability to the shoulder joint
Which bones make up the elbow joint?
The humerus articulates with the ulna
Which characteristics of the elbow joint provide stability? (3)
- Stability is provided by close fit of the trochlea (on humerus) and trochlear notch (on ulna). This is again based on how the articular surfaces fit together.
- 2 ligaments
- Muscle and tendon of arm muscles wrap around elbow to provide further stability
What structures determine elbow movement?
Articular capsule is thin and loose, which allows flexion/extension movement
Ulnar collateral ligament (medial) and radial collateral ligament (lateral) prevent side to side movement
Which 2 ligaments are associated with the elbow joint?
Ulnar collateral ligament (medial) and radial collateral ligament (lateral)
Which bones compose the coxal joint?
The head of the femur articulates with the os coxa. This is a ball and socket joint
Which factors contribute to the stability of the coxal joint?
- Shape- this is a ball and socket joint and has a deep socket. The acetabulum of the os coxa has acetabular labrum to further deepen the socket
- The joint is reinforced by strong ligaments. The ligaments twist themselves completely around the joint
Ligaments of the articular capsule of the coxal joint (3)
- Iliofemoral ligament
- Pubofemoral ligament
- Ischiofemoral ligament
Ligamentum teres
Ligament of the head of the femur. This is not found in the glenohumeral joint. Attaches to the head of the femur on the inside of the joint and extends to the inner surface of the acetabulum.
Ligamentum teres function
Function is unclear- probably serves as a coxal joint stabilizer for certain movement of the joint, like flexion or rotation. It also allows for blood and nerve supply to the head of the femur. People who damage this ligament tend to have severe arthritis at this joint- damage causes less synovial fluid and cartilage
Joints found in the knee joint (3)
- Femoropatellar joint
2. Tibiofemoral joints- there are 2 of these, lateral and medial
Femoropatellar joint
The joint between the patella and femur- it’s a plane joint (intermediate to the other two joints)
Tibiofemoral joints
Two joints between the femur and tibia (lateral and medial). It’s a hinge joint allows flexion/extension
Joint capsule of the knee joint
The joint is only partially closed by joint capsule- anterior surface of the knee has no capsule, it is enclosed with ligaments
Important features of the knee joint (3)
- Menisci
- Extracapsular and capsular ligaments
- Intracapsular ligaments (cruciate ligaments)
Menisci
C-shaped joint cartilage of the knee. They form ridges laterally and medially and help with absorbing shock.
How can the menisci be damaged?
Only attached to the tibia along the outer margins of the bone, the rest is unattached. Therefore, it can tear or rip away easily. This is a very common sports injury, especially with sudden or lateral movements. Usually needs surgery to fix it
Extracapsular and capsular ligaments
Extracapsular and capsular ligaments prevent hyperextension of the knee. If you could freely hyperextend your knee, it would bend backwards.
Cruciate ligaments
Intracapsular ligaments of the knee joint. They secure articulating bones, prevent displacement. Named according to where they attach to the tibia.
Cruciate ligaments of the knee joint (2)
- Anterior cruciate ligament
2. Posterior cruciate ligament
Anterior cruciate ligament (ACL)
Ligament that prevents forward sliding of tibia and prevents hyperextension. It attaches to the tibia on the anterior side.
The ACL is smaller and thinner and therefore tears more easily, so it’s more of a problem than the PCL.
What causes damage to the ACL?
This is also a very common sports injury caused by sudden changes in direction
Treatment- ranges from time and immobilization to never being able to play sports again
Posterior cruciate ligament (PCL)
Ligament that prevents backward sliding of tibia and forward sliding of femur. It attaches to the tibia on the posterior side
Factors that can cause joint injuries (3)
- Overusing your joints- excessive pressure and stress will cause damage. Often caused by people in a manual labor profession like construction workers
- Not using your joints- the joints are not maintained, like people who work office jobs and sit all day
- Using your joints the wrong way- trying to force a movement or doing something like weight lifting the wrong way
Cartilage tears
Joint cartilage (usually menisci) is overstretched, can snap and break. Healing (if any) takes time. Thick cartilage will probably have too much damage and not be able to heal through diffusion (cartilage is avascular). The joint is less stable after injury
What forces can cause cartilage tears?
Compression (pushing together) and shear stress (rubbing against each other) occur simultaneously. This will rip cartilage if it occurs at the same time.
Locking
Pieces of broken cartilage from cartilage tears can interfere with joint function, called “locking”.
Sprains
Ligaments reinforcing joint are damaged. There are 2 types: a partial/stretch tear and a completely torn ligament
Stretch/partial tear
A type of sprain where the ligament is capable of healing on its own. Similar to cartilage, this is a slow process
Completely torn ligament treatments (3)
This is a type of sprain- more difficult to repair. Treatments:
- Time/immobilization
- Sew ends of the ligament together (basically like trying to sew spaghetti together- very difficult)
- Grafting- taking a piece of tendon and using it to replace the torn ligament
Subluxations
Incomplete/partial dislocation of a joint
Dislocations
Occurs when the joint comes out of alignment. You can dislocate any synovial joint, but stable joints take more stress to dislocate
Which joints are more likely to dislocate?
Less stable joints
Why are joints that have already been dislocated more likely to dislocate again in the future?
The ligaments have been overstretched and will remain overstretched when the joint is put back in place- the joint will be less stable than before
How is arthritis categorized? (2)
- Pathophysiology (degenerative or inflammatory)
2. Time of onset (acute or chronic)
Inflammatory arthritis
The joint tissue is inflamed, swollen, and painful. Rheumatoid arthritis is an example
Degenerative arthritis
Losing joint tissue and not replacing it with anything. Eventually the bones are rubbing together- this is very painful. Osteoarthritis is an example.
What causes acute arthritis?
Bacterial, inflammatory- easily treated with antibiotics
Chronic arthritis
Inflammatory/degenerative, long lasting
Osteoarthritis
Most common form of chronic arthritis- progresses slowly and is irreversible. More articular cartilage is destroyed than can be replaced by the body- exposed bone tissue rubs together, forming bone spurs. Poorly aligned and/or overused joints are most likely to exhibit OA
Bone spurs
Bone spurs are permanent bone deformities.
Osteoarthritis deforms bone ends (excessive growth of bone in strange places) and restricts movement at joint because it gets in the way.
Bone spurs aren’t always necessarily a result of osteoarthritis, however.
Who is more commonly affected in osteoarthritis?
Older individuals are more affected than other age groups, and more women are affected than men
Osteoarthritis treatment
Treatment- pain medication or complete joint replacement surgery. The ends of the epiphyses are cut off and covered with metal.
What can be done to make a joint more stable?
Strengthening a muscle around a joint will make it more stable
Rheumatoid arthritis
Autoimmune chronic inflammatory disorder (immune system is attacking your joints). Bilateral degenerative condition (occurs in the same joints on both sides). Individuals affected have flare ups followed by periods of remission (mostly symptom free). It never goes into a permanent period of remission, however, and flare ups will usually get worse over time.
Which joints are most likely to be affected by rheumatoid arthritis?
Joints of fingers, wrist, ankles, feet most likely to be affected.
Symptoms of rheumatoid arthritis
Pain and swelling felt in joints affected by RA
Who is more commonly affected by rheumatoid arthritis?
More women affected than men, typically diagnosed between ages 30-50
Progression of rheumatoid arthritis (3 stages)
- Synovial membrane becomes inflamed
- Lymphocytes and macrophages flood area to destroy the cause of inflammation
- Accumulation of synovial fluid and formation of a pannus
What occurs during the lymphocyte/macrophage stage of rheumatoid arthritis?
Release chemicals in such a large amount that it destroys healthy tissue
Macrophages also destroy some of the synovial membrane
Pannus
a thickened portion of the synovial membrane as a result of rheumatoid arthritis- breaks down cartilage tissue over time
Ankylosis
Occurs with rheumatoid arthritis- scar tissue forms where the hyaline cartilage tissue once was, fusing bones together
Treatment of rheumatoid arthritis
No cure, but can be treated with painkillers or steroids (immune system depressants)
