Synovial Joints (Lecture)

A joint is a point of contact between:

o Two or more bones

o Cartilage and bone

o Teeth and bone

Joints can be classified:

o Structurally

- Is there a joint cavity?

- What type of connective tissue is involved?

o Functionally

- Range of motion at joint (none, limited, extensive)

fibrous joints

- Fibrous Joints

o Lack synovial cavity.

o Articulating bones are head together with dense fibrous connective tissue.

o Permit little or no movement.

o Types:

§ Sutures

§ Syndesmoses

§ Interosseous membranes

sutures

o dense fibrous connective tissue (CT)

§ Ex. Suture

syndesmoses

o more dense fibrous CT than a suture.

§ Ex. Gomphosis

synostosis

- the early growing together or fusion of two or more bones of the skull.

§ Frontal bones.

interosseous membranes

a broad sheet of dense fibrous CT.

§ Ex. Between radius and ulna

Discriminator between sutures and syndesmoses is

the space between articulating structures.

cartilaginous joints

o Lack synovial cavity.

o Articulating bones are held together with cartilage connective tissue.

o Permit little or no movement.

o Types of cartilaginous joints:

§ Synchondroses

§ Symphyses

synchondrosis

o hyalin cartilage; no movement.

§ Ex. Epiphyseal plate.

symphysis

o fibrocartilage; some movement.

§ Pubic symphysis

synovial joints

- Synovial Cavity

- Articular Cartilage

- Held together by ligaments.

- Contain synovial fluid.

- Nerve and blood supply.

- Surrounded by an articular capsule.

- Permit a large range of movement.

synovial cavity

space between bones at a synovial joint; contains synovial fluid produced by the synovial membrane

fibrous membrane of synovial cavity

- denser connective tissue (outside)

synovial membrane

membrane lining the capsule of a joint. - where synovial fluid is produced and secreted

- composed of areolar connective tissue with collagen and elastic fibers.

synovial fluid

joint-lubricating fluid secreted by the synovial membrane.

- hyaluronic acid

- gel like clear or yellow fluid

Articular Cartilage

hyaline cartilage that covers ends of bones in synovial joints

Articular capsule

Fibrous envelope that encloses a synovial joint

- Surrounds a synovial joint, encloses the articular cavity, and unites the articulating bones. The articular capsule is composed of two layers, an outer fibrous layer and an inner synovial membrane.

what are found at many synovial joints?

Bursae and tendon sheaths

bursae

o sac-like structures filled with synovial fluid.

§ Cushion movement of one body part over another.

§ Occur between skin and bone, tendon and bone, muscle and bone and ligaments and bone.

§ Compromised of outer membranous layer and inner synovial layer may communicate with the joint cavity in which case their synovial membranes are continuous.

tendon sheaths

o a tube-like bursae that wraps around tendons.

§ Subject to a great deal of friction.

§ Ex. Transverse humeral ligament.

§ Have an inner (visceral) and outer (parietal) layer with thin film of synovial fluid between.

§ Occur where tendons pass through synovial cavity, wrist, ankles, toes, and fingers.

menisci

Inside some synovial joints, such as the knee, crescent-shaped pads of fibrous cartilage lie between the articular surfaces of the bones and are attached to the fibrous capsule.

- provide additional shock absorption

- provide better fit between articulating surfaces of bones

plane joint

short slipping or gliding movements

- Uniaxial

- between navicular and second and third cuneiforms of tarsus in foot + carpals

- distal ends of radius and ulna

hinge joint

Joint between bones (as at the elbow or knee) that permits motion in only one plane (flexion and extension).

- Uniaxial

- between trochlea of humerus and trochlear notch of ulna at the elbow.

pivot joint

internal and or external rotation of bone turns around an axis (supination and pronation)

- Uniaxial

- between head of radius and radial notch of ulna.

condyloid joint

synovial joint that does everything except rotating (flexion + extension and adduction + abduction)

- biaxial

- between radius and scaphoid and lunate bones of carpus (wrist).

saddle joint

- allows opposition (especially in the thumb)

- Biaxial

- between trapezium of carpus (wrist) and metacarpal of thumb.

ball and socket joint

o Triaxial

- between head of femur and acetabulum of hip bone.

- shoulder joint

factors affecting contact and ROM at synovial joints

- structure and shape of articulating bones

- strength and tautness of joint ligaments

- arrangement and tension of the muscles

- contact of soft parts

- hormones

- disuse

structure and shape of articulating bones

§ The structure or shape of the articulating bones determines how closely they can fit together. The articular surfaces of some bones have a complementary relationship.

§ Ex) whether joint is concave and convex.

strength and tautness of joint ligaments

§ The different components of an articular capsule are tense or taut only when the joint is in certain positions. Tense ligaments not only restrict the range of motion but also direct the movement of the articulating bones with respect to each other.

§ The more flexibility the more range of motion.

arrangement and tension of the muscles

§ Muscle tension reinforces the restraint placed on a joint by its ligaments, and thus restricts movement.

§ Muscles need to cross the joint for there to be action.

§ If muscles are tight it limits range of motion.

§ This is why it's important to stretch (releases tension).

contact of soft parts

§ The point at which one body surface contacts another may limit mobility.

§ Joint movement may also be restricted by the presence of adipose tissue.

· If there is more soft tissue, limits range of motion.

hormones

§ For example, relaxin, a hormone produced by the placenta and ovaries, increases the flexibility of the fibrous cartilage of the pubic symphysis and loosens the ligaments between the sacrum, hip bone, and coccyx toward the end of pregnancy.

disuse

§ Movement at a joint may be restricted if a joint has not been used for an extended period of time.

§ Atrophy- A reduction in size or wasting muscle.

· Less amount of muscle tissue means less work.

§ Tendons and ligaments become more stiff (less flexible) which limits ROM.

the shoulder complex: sternoclavicular joint

- sternoclavicular ligament

- costoclavicular ligament

- scapulothoracic joint

sternoclavicular ligament

· Connects clavicle to the manubrium.

· Anterior and posterior ligaments.

costoclavicular ligament

· Extends from the clavicle to the first rib.

scapulothoracic joint

§ (not a true joint)

· Articulation of anterior surface of scapula with posterior thorax (ribs 2-7).

the shoulder complex: Glenohumeral Joint

· Ball-and-socket joint

o Glenohumeral ligament

o Coracohumeral ligament

o Coracoclavicular ligament

o Coracoacromial ligament

o Acromioclavicular ligament

glenohumeral ligament

§ Connects humerus to the glenoid cavity.

coracohumeral ligament

§ Connects head of humerus to the coracoid process.

coracoclavicular ligament

§ Connects the clavicle to the coracoid process.

coracoacromial ligament

§ Makes connection between coracoid process and the acromion.

acromioclavicular ligament

§ Connects the clavicle to the acromion.

glenohumeral joint bursae: subdeltoid bursa

o Forms a cushion between the deltoid muscle and the greater tuberosity when the arm is abducted.

glenohumeral joint bursae: subacromial and subcoracoid bursae

o Form a cushion between the acromion/coracoid process and the joint capsule.

rotator cuff muscles

supraspinatus, infraspinatus, teres minor, subscapularis

as we age, our joints experience:

§ Decreased production of synovial fluid.

§ Thinning of articular cartilage.

· Left with ends of bone to ends of bone.

· Caused by osteoarthritis.

§ Loss of ligament length and flexibility.

arthroplasty

surgical repair of a joint

partial hip replacement

involves only the femur

total hip replacement

surgical procedure to replace a hip joint damaged by a degenerative disease, commonly arthritis. - Involve both the acetabulum and head of the femur.

partial knee replacement

- also called a unicompartmental knee replacement, only one side of the knee joint is replaced

total knee replacement

the damaged cartilage is removed from the distal end of the femur, the proximal end of the tibia, and the back surface of the patella (if the back surface of the patella is not badly damaged, it may be left intact).

osteoarthritis

§ : loss of articular cartilage.

· No specific cause.

· Mitigating factors: increased age, damage to joint, muscle injury around the joint, repetitive use.

· Affects larger joints first and more rapidly (knee and hip joints).

· Non-inflammatory

· Affects mobility.

rheumatoid arthritis

§ autoimmune

· Immune system is attacking synovial joint space.

· Inflammatory process.

· Still attacking articular cartilage and synovial cavity.

· Hits smaller joints first.

· The fibrous tissue ossifies and fuses the joint so that it becomes immovable—the ultimate crippling effect of RA.

· Treatment: slow the immune system from what its doing.

gouty arthritis

· Inflammatory arthritis.

· Sodium urate crystals are deposited in the soft tissues of the joints. Gout most often affects the joints of the feet, especially at the base of the great (big) toe. The crystals irritate and erode the cartilage, causing inflammation, swelling, and acute pain. Eventually, the crystals destroy all joint tissues. If the disorder is untreated, the ends of the articulating bones fuse, and the joint becomes immovable.

· Treatment: Pain relief followed by administration of allopurinol to keep uric acid levels low so that crystals do not form.

lyme disease

§ The bacteria are transmitted to humans mainly by deer ticks (Ixodes dammini). These ticks are so small that their bites often go unnoticed. Within a few weeks of the tick bite, a rash may appear at the site. Although the rash often resembles a bull's-eye target, there are many variations, and some people never even develop a rash. Other symptoms include joint stiffness, fever and chills, headache, stiff neck, nausea, and low back pain. In advanced stages of the disease, arthritis is the main complication. It usually afflicts the larger joints such as the knee, ankle, hip, elbow, or wrist. Antibiotics are generally effective against Lyme disease, especially if they are given promptly. However, some symptoms may linger for years.

sprain

§ the forcible wrenching or twisting of a joint that stretches or tears its ligaments but does not dislocate the bones.

strain

§ is a stretched or partially torn muscle or muscle and tendon. It often occurs when a muscle contracts suddenly and powerfully—such as the leg muscles of sprinters when they spring from the blocks.

treatment for sprains + strains: PRICE

§ protection, rest, ice, compression, elevation

protection

· Protecting from further injury/ use splints, padding, sling, etc.

rest

· Stop activity to avoid further damage to tissues.

ice

· Ice slows blood flow to area which reduces swelling and relieves pain/ decrease inflammation.

compression

· Use a wrap or bandage to reduce swelling/ compress but not block blood flow.

elevation

· The injured area above the level of the heart, when possible, will reduce potential swelling/ get gravity to work in favor.

o Lowers the pressure in local blood vessels and helps to limit the bleeding.

tenosynovitis

§ Inflammation of the tendons, tendon sheaths, and synovial membranes surrounding certain joints. The tendons most often affected are at the wrists, shoulders, elbows (resulting in tennis elbow), finger joints (resulting in trigger finger), ankles, and feet. The affected sheaths sometimes become visibly swollen because of fluid accumulation. Tenderness and pain are frequently associated with movement of the body part. The condition often follows trauma, strain, or excessive exercise. Tenosynovitis of the dorsum of the foot may be caused by tying shoelaces too tightly. Gymnasts are prone to developing the condition because of chronic, repetitive, and maximum extension at the wrists.

dislocated mandible

§ The displacement of a bone from a joint with tearing of ligaments, tendons, and articular capsules.

dislocated mandible: anterior displacement

§ the most common and occur when the condylar processes of the mandible pass anterior to the articular tubercles. Common causes are extreme mouth opening, as in yawning or taking a large bite, dental procedures, or general anesthesia.

dislocated mandible: posterior displacement

§ can be caused by a direct blow to the chin.

dislocated mandible: lateral displacement

§ usually associated with mandibular fractures.

dislocated mandible: superior displacement

§ typically caused by a direct blow to a partially opened mouth.

subluxation

- Partial dislocation

- Something pulls your joint apart and the bones still touch, just not as completely.

- Can occur usually in kneecap, hip, finger, elbow, shoulder.

- Ex) nursemaid elbow

nursemaid elbow

Common injury among toddlers and preschoolers. It happens when a ligament slips out of place and gets caught between two bones in the elbow joint.

nursemaid elbow cause + ages

- Sometimes during play or when they're lifted by the arm, two bones in the elbow can briefly separate a little bit. This can let a ligament slip into the joint, which then gets stuck. As kids get older, the ligament tightens. Most won't get nursemaid's elbow after age 5, though it can happen up to age 6 or 7.

nursemaid treatment

- Gentle arm move called reduction to get ligament out from between two bones.

elbow joint (hinge joint)

humeroradial + humeroulnar joints