1. JOINTS

2. Objectives
Identify the bones that articulate at different joints in the body.
Name the 6 types of synovial joint and give examples of each.
Describe the structure and function of parts of a synovial joint.
Be able to classify joints according the movement they allow.
Use technical language to describe common joint movements.
Analyse sporting techniques in terms of joint movements.

3. The human skeleton consists of 206 bones
The human skeleton consists of 206 bones. Many of which move or hinge at joints. In conjunction with over 600 muscles these bones enable the human body to achieve a variety of movements.
The functions of the skeletal system include: -
To provide a lever system against which muscles can pull.
To provide a large surface area for the attachment of muscles.
To protect delicate organs such as the brain.
To give shape to the body.
To give support to the body.
To manufacture red blood cells and to store fat calcium and phosphate.

4. AXIAL & APPENDICULAR SKELETON
The bones of the body are grouped into two major divisions.
The axial skeleton consists of the bones, which lie around the longitudinal axis of the body. These include the SKULL, VERTEBRAL COLUMN, STERNUM & RIBS.
The appendicular skeleton consists of the bones of the LIMBS, PECTORAL (shoulder) GIRDLE, & PELVIC (hips) GIRDLE.

5. JOINTS Joints are where two or more bones articulate (move).
Joints are classified according to how much movement they allow.
1. Fibrous – these are fixed or immovable joints such as the cranium, sacrum and the coccyx.
2. Cartilaginous – these are slightly movable joints such as the vertebrae.
3. Synovial – these are freely movable joints such as the shoulder and hip.

6. Synovial joints In PE these are the most important joints.
There are 6 types of synovial joint.
1. Ball & socket – hip and shoulder.
2. Hinge – knee, elbow and ankle.
3. Pivot – radio-ulna, atlas/axis.
4. Saddle – thumb.
5. Condyloid – wrist.
6. Gliding – between vertebrae in spine.

7. Ball & socket joints The hip joint
The head of the femur fits into a deep cavity called the acetabulum on the pelvic bone.
This deep cavity gives the hip joint stability.
The presence of strong ligaments add to the stability making it difficult to dislocate the hip.

8. The shoulder joint
The head of the humerus fits into a shallow cavity on the scapula called the glenoid fossa.
The shoulder is the most mobile joint in the body but is also fairly unstable because of the shallow cavity.
Stability is improved by ligaments and muscles.

9. Hinge Joints The knee joint
In the knee joint the femur articulates with the tibia.
The patella (knee cap) helps to give a better angle of pull.
The fibula is not part of the knee joint and so the tibia is the weight bearing bone.

10. The elbow joint
In the elbow the humerus articulates with the radius and the ulna.
Movement can only occur in one plane.
The ankle joint
In the ankle the talus articulates with the tibia and fibula.
Ligaments provide stability to the joint.

11. The pivot joint The radio-ulna
In this joint the radius and ulna articulate within the elbow joint.
This joint allows the elbow some twisting movement (pronation & supination.
Atlas/axis
In this joint the atlas and axis bones articulate to allow a rotation movement as in shaking your head.

12. Condyloid and gliding joints
The spine
The spine has five areas and has to fulfil many functions such as weight bearing stability and support.
There are three type of joint in the spine but for A level the main one to know is the gliding joints between the vertebral arches.
The wrist
In this joint the radius and ulna bones articulate with 3 of the carpal bones.

13. Features of a synovial joint
Synovial joint have a number of common features.
FEATURE
STRUCTURE
FUNCTION
Hyaline/articular cartilage
Smooth& spongy covers ends of bones
Prevents friction between articulating bones
Two layered joint capsule
Outer layer – tough & fibrous
Inner – synovial membrane covers all internal surfaces
To strengthen joint
To secrete synovial fluid
Synovial fluid
Slippery fluid like egg white which fills joint capsule
Reduce friction
Nourish cartilage
To get rid of waste from joint

14. FEATURE
STRUCTURE
FUNCTION
Ligament
A band of strong fibrous connective material
Joins bone to bone
Provides stability
Pads of fat
Fatty pad found between capsule, bone or muscle
Increases joint stability
Acts as shock absorber
Reduces friction
Meniscus
A wedge of tough flexible cartilage
Improves fit between bone ends
Increases stability
Reduces wear & tear to joint surfaces
Bursae
Fluid filled sac found between tendon and bone

15. Movements around a joint
All synovial joints can move freely but the amount and type of movements which occur at each joint varies.
Many of the movements occur in pairs – they are the opposite of each other.
Technical terms to describe the movements you need to know include:-

16. TERM
MEANING
FLEXION
A decrease in the angle that occurs in a joint
EXTENSION
An increase in the angle which occurs at a joint
ABDUCTION
Movement away from the midline of the body
ADDUCTION
Movement towards the midline of the body
ROTATION
Movement of a bone around its axis (can be inward (medial) or outward (lateral))
CIRCUMDUCTION
Lower end of bone moves around in a circle
LATERAL FLEXION
Bending sideways
PLANTAR FLEXION
Pointing the foot downwards
DORSIFLEXION
Bending the foot upwards towards tibia
PRONATION
Facing the palm of the hand down
SUPINATION
Facing the palm of the hand up

17. JOINT POSSIBLE MOVEMENTS SHOULDER
Flexion & extension, adduction & abduction, circumduction, rotation
ELBOW
Flexion & extension
RADIO-ULNA
Pronation & supination
WRIST
Flexion & extension, adduction & abduction, circumduction
SPINE
Flexion & extension, lateral extension, rotation
HIP
KNEE
ANKLE
Dorsiflexion & plantaflexion