Is it Okay to Crack Your
Knuckles?
https://www.youtube.com/watch?v=TIBydD49-xM
Joint Facts
Joints - are places where two bones meet
 There are 400 + joints
 Approximately 230 movable and semi-
movable joints
 Muscles span joints, crossing from 1 bone to
another
 When muscles contract, they tug on the
bones, producing movement at the joint
Cartilage
There are three types:
1. Hyaline
2. Fibrous and
3. Elastic
Hyaline cartilage:
 Covers the ends of bones
 Cushions and reduces friction during movement
 Key to preventing wear and tear on joints
Knee Joint
Ligaments
Ligaments - Connects bone to bone




Bands of tough, fibrous collagen and stretchy elastin
Bind joints to help strengthen and stabilize
Permit movement in certain directions
Also support organs, such as the liver and bladder
Knee Joint
Tendons
Tendons – Connect muscle to bone.
 When a muscle contracts, it pulls on a tendon, which
then tugs on the attached bone
 Also help stabilize joints
Achillies Tendon
Types of Joints
 Immovable - cranium
 Hinge – elbow, knee, jaw
 Pivot – head/neck, elbow
 Ellipsoidal - hand/wrist, foot/ankle
 Ball and socket – shoulder, hip
 Saddle – knuckles, thumb, wrist
 Gliding – hand, foot
Joints continued……
 Ligaments join with
other connective tissue to
form a joint capsule,
enclosing the moveable
joint
 The joint capsule is lined
with a membrane that
secretes synovial fluid,
which acts as a
lubricating substance
Clinical Conditions
Gigantism
 Childhood hyper secretion of
growth hormone by the pituitary
gland causes excessive growth.
Tallest Man Ever: Robert Wadlow – 8
ft 11 inch
Pituitary dwarfism
 Growth hormone deficiency in
children resulting in extremely
short long bones and maximum
stature of 4 feet.
 Shortest man:
http://www.usatoday.com/story/news/nation
-now/2015/09/04/shortest-man-world-hasdied/71743044/