Synovial Joints: Anatomy and ROM factors

What is the anatomy of a synovial joint?

(outer to inner)

i) articular capsule 

• outer fibrous membrane 

• inner synovial membrane

ii) articular cartilage 

iii) synovial fluid 

What is the articular capsule?

surrounds the synovial joint, encloses the synovial cavity, and unites articulating bones

What are the two membranes of the articular capsule?

outer fibrous membrane and inner synovial membrane

(AC) What does the outer fibrous membrane attach to? Where? What is its function?

fibrous tissue attaches to the periosteum of articulating bones

provides movement at joint and great tensile strength, preventing dislocation

(AC) What is the inner synovial membrane? What is its function?

vascular layer of serous connective tissue. it absorbs and secretes synovial fluid and mediates the nutrient exchange between blood and joint.

What is articular cartilage? Where is it located? What is its function?

layer of hyaline cartilage within the articular capsule, covering the surfaces of articulating bones.

minimizes friction upon joint movement, and absorbs shock

Synovial fluid is secreted by? Where is it located?

secreted by the synovial membrane (AC) and is a thin film over articular capsule surfaces

Synovial fluid consist of? 

hyaluronic acid and interstitial fluid

What is hyaluronic acid secreted by? Interstitial fluid?

secreted by synovial cells in the synovial membrane

fluid filtered by blood plasma

What are the functions of synovial fluid?

lubricates joints, reducing friction and absorbing shock

nutrient distribution to chondrocytes within articular cartilage and removes wastes (CO2, metabolic)

phagocytosis of microbes and debris

articular surfaces of synovial joints contact one another and determine the type and possible?

range of motion

what is range of motion?

degree of a circle that the bones of a joint can move

What are the factors affecting contact and range of motion of synovial joints?

1) structure or shape of articulating bones 

2) strength and tension of joint ligaments 

3) arrangement and tension of muscles 

4) contact of soft parts

5) hormones

6) disuse

1) structure or shape of articulating bones 

function follows structure

2) strength and tension of joint ligaments 

different components of a fibrous capsule are tense when joint is in an certain position, restricting ROM and directing movement of articulating bones

3) arrangement and tension of muscles 

muscle tension reinforces the restraint on joints by ligaments, restricting movement 

4) contact of soft parts

a body surface contacting another may limit mobility

ex) lots of muscle or adipose tissue

5) hormones

joint flexibility may be affected by hormones

ex) relaxin produces by placenta in ovaries, increases the flexibility of the fibrocartilage is the pubic symphysis

6) disuse

when joint hasn’t been moved in an extended period it may result in a decrease amount of synovial fluid, lost flexibility of ligaments and tendons, and muscle atrophy

What is bursa?

saclike structures that consist of an outer fibrous membrane and thin dense connective tissue lined by a synovial membrane

What is the function of bursa?

reduce friction during movement, strategically placed to alleviate friction around some joints