Joint stability, Support and Movement Flashcards
what are the 3 different classifications of joints?
Fibrous joints
Cartilaginous joints
Synovial joints
define fibrous joints
give examples
Definition: Where neighbouring bones are joined together by a dense irregular connective tissue (Collage fibres run transversely and longitudinally)
Fibrous joints provide stability and protect structures
They do not allow for movement
Examples:
Skull sutures
Syndesmosis: bones united by a sheet of fibrous tissue, ligament, or a membrane (e.g. Interosseus membrane between radius and ulna) (all dense irregular CT). This can’t be seen on skeletal models
Gomphosis: Joint between a tooth and a socket.
define cartilaginous joints
give examples
Definition: where neighbouring bones are joined together by cartilage
The bones are further apart than in fibrous joint
Two Categories
Primary cartilaginous joints: (synchondrosis)
Bones are united by hyaline cartilage.
Usually a temporary joint (appear during development) present during the growth of a long bone.
Secondary cartilaginous joint:
Articular surface of the bone is coated with Hyaline cartilage.
The Bones are united by strong fibrocartilage.
Strong joints allowing slight movements e.g., between vertebrae, pubic symphysis
define synovial joints
give examples
Most common joints in the skeleton
Multiple Types
Provide a large range of movements
Many have specialised features e.g.:
Articular discs (fibrocartilage pads): act as a shock absorber to help prevent damage to bones e.g. in the Temporomandibular joint.
Fibrocartilage ring (aka labrum): Present to help deepen the bony articulation at a joint. This is important as the greater bony articulation present at a joint the more stable the joint is the less chance there is of a dislocation.
E.g., Glenoid labrum at shoulder. This allows for a better articulation of between humerus and the scapula.
Tendons passing through the joint capsule to help attach muscle to bone
E.g. biceps Brachii at shoulder
what are the 6 common features of synovial joints?
- Bone ends covered by articular cartilage
- Joint has a connective tissue capsule
- Joint cavity – only present in synovial joint
- Inner surface of capsule is lined by synovial membrane (secretes synovial fluid to fill the joint cavity)
Synovial fluid lubricates the joint to help prevent bone on bone erosion during movement. - Commonly reinforced by ligaments
- Allow a wide range of movements
what are 2 specialised synovial joints
hip and knee joint
what is the hip joint made of?
The hip joint is a deep ball and socket joint
It consists of an articulation of the innominate bone (socket) with the head (ball) of the femur
The bony articulation is a lot deeper than other bones making it very hard to dislocate.
A ligament located on the head of femur helps to fix it to its socket - it provides stability.
what is the knee joint made of?
names of the ligaments?
It consists of an articulation of the lower end of femur with the upper aspect of the tibia.
The knee joint is a weight-bearing joint - bears weight from the upper aspect of the body.
Therefore, the meniscus (piece of cartilage) and the articular cartilage act as shock absorber as the knee joint.
They also help prevent damage by stopping the bones at the joint from grinding together.
what is the shoulder joint made up of?
Synovial Ball and Socket Joint
Articulation between humeral head and the glenoid cavity of the scapula
Bony stability at the shoulder is sacrificed to enable a wide range of movements of the upper limb – therefore shoulder joint dislocation is common.
what is the structure of the right humerus (anterior)?
Head – The humeral head is much smaller than the femoral head which is why bony articulation is not as extensive and so why it is more prone to dislocation
Greater and lesser tuberosity allow for the attachment of muscles and ligaments to help protect and support shoulder joint.
Intertubercular groove – which allows for passage of structures such as ligaments in and around shoulder joint.
what is the structure of the right scapula (anterior)?
Scapula lies on the back of the rib cage
The subscapular fossa lies very close to the ribs
Coracoid process and the acromion allow for attachment of muscles and ligaments
Glenoid cavity is what articulates with head of humerus.
what is the structure of the right scapula (posterior)?
Acromion is a continuation of spine of scapula
Spine of scapula splits the posterior aspect of scapula into 2 separate fossa
Above the spine => supraspinous fossa
Below the spine => infraspinous fossa.
what are the 3 shoulder joint ligaments?
These helps to stabilise joints:
Acromioclavicular ligament – runs from acromion to clavicle
Coracoclavicular ligament - runs from coracoid process to clavicle.
Coracoacromial ligament - - runs from coracoid process to acromion
These ligaments are small so don’t have a great role at maintaining stability at shoulder joint.
what is the Glenoid Labrum?
Its at shoulder joint
The Glenoid Labrum is a fibrocartilaginous ‘lip’ around the glenoid cavity
It acts to deepen the cavity for better articulation with humeral head and glenoid cavity, which helps support and stabilise the shoulder joint
The most important structure for stability at the shoulder joint are the muscles of the shoulder region
what are the 3 muscles of the anterior shoulder region?
Deltoid Muscle
Pectoralis Major
Pectoralis minor
deltoid muscle origin, insertion, innervation, movement
Innervated by the axillary nerve
Runs from the clavicle, acromion and spine of scapula to insert into the deltoid tuberosity of the humerus
It is important in bringing the humeral head very close into articular surface of scapula.
Facilitates flexion, extension, abduction and medial and lateral rotation.
pectoralis major muscle origin, insertion, innervation, movement
Innervated by the Lateral and Medial Pectoral Nerves
Attached to clavicle, sternum and upper ribs, tendon and inserts into the intertubercular groove of the humerus.
When the muscle contracts it pulls the humeral head into the glenoid cavity.
trapezius muscle origin, insertion, innervation, movement
Innervated by Accessory Nerve
Runs from the vertebral column and external occipital protuberance to clavicle, acromion and spine of scapula.
Facilitates bracing and shrugging shoulders
latissimus dorsi muscle origin, insertion, innervation, movement
Runs from thoracolumbar fascia, iliac crest, lower 6 thoracic vertebrae and lower 3 or 4 ribs to insert its tendon in intertubercular groove of the humerus
Facilitates extension, adduction, medial rotation.
name the 4 rotator cuff muscles
what is the function of rotator cuff muscles?
As well as the superficial back and chest muscles the shoulder region contains the ROTATOR CUFF, a specialised muscle group which FIXES the head of the humerus into the glenoid cavity.
This is their essential role.
The 4 Rotator cuff muscles fully surrounds the scapula:
Subscapularis
Supraspinatus
Infraspinatus
Teres Minor
Subscapularis muscle origin, insertion, innervation, movement
Innervated by the Upper and Lower Subscapular Nerve
Runs from subscapular fossa to lesser tuberosity of humerus.
Facilitates medial rotation and adduction
Provides support to shoulder joint from in front
Supraspinatus muscle origin, insertion, innervation, movement
Innervated by Suprascapular nerve
Runs from supraspinous fossa to greater tuberosity of humerus.
Facilitates abduction
Provides support to shoulder joint from above
Infraspinatus muscle origin, insertion, innervation, movement
Innervated by suprascapular nerve
Runs from infraspinous fossa to greater tuberosity of humerus.
Facilitates lateral rotation
Provides support to shoulder joint from below
teres minor muscle origin, insertion, innervation, movement
Innervated by axillary nerve
Runs from lateral border of scapula to greater tuberosity of humerus.
Facilitates lateral rotation
Provides support to shoulder joint from behind
explain how shoulder joint dislocation occurs
Articulation between the humerus and glenoid cavity is poor, (not great area of bony articulation) so the shoulder is a commonly dislocated large joint
The Humeral head rarely moves upwards during dislocation due to the presence of the coracoid process
So, dislocation of humeral head usually occurs inferiorly, with head lying in a sub-coracoid position.
During dislocation the humeral head can also move towards the midline due to the muscles attached to the humerus.
After a dislocation the inappropriate positioning of humerus can cause damage to soft tissue –> tears joint capsule and can damage Axillary Nerve (which winds around upper aspect of humerus)
Damage to Axillary Nerve results in loss of sensation to skin over deltoid muscle: ‘Regimental Badge’ sign.
explain the articulation of the elbow joint
A synovial hinge joint
3 bones
Articulation between the distal end of the humerus and proximal ends of the radius and ulna
Medial side of humerus
Trochlea (part of the lower aspect of the humerus) articulates with the coronoid process of the ulna.
Lateral side
Capitulum (part of the lower aspect of the humerus) articulates with the radial head of the radius.
what are the 3 ligaments of the elbow joint?
Ligaments for stability:
Medial Ligament holds Ulna (most medial bone) in place
Lateral Ligament holds Radius in place
Annular Ligament holds Radius in place
what is a “pulled elbow”?
subluxation of the head of the radius (dislocation of elbow joint)
Radial head held in place by ring like Annular Ligament is softer in children, hence more prone to dislocation. Why you don’t pull children up by their arm.
what does the muscular compartment of the upper arm contain?
Anterior Muscle flexors
Posterior Muscle Extensors
what are anterior muscle flexors?
function?
Anterior Muscle flexors: Muscle group that mediates flexion at elbow
2 Elbow Flexors
1) Biceps Brachii
Arises from 2 heads:
long head from supraglenoid tubercle
short head from coracoid process
Both heads unite to one large muscle belly at the anterior side of the humerus and attach to the radial tuberosity.
2) Brachialis
Arises from humeral shaft and inserts into tuberosity of ulna
Both the Biceps Brachii and the Brachialis are innervated by Musculocutaneous Nerve
what are posterior muscle extensors?
function?
Posterior Muscle Extensors: Muscle group that mediates extension at elbow
Triceps Brachii
Arises from 3 heads:
lateral head: comes from superior, lateral margin of humerus
long head: from infraglenoid tubercle of scapula
medial head: from posterior surface of humerus
All Inserts into Olecranon of Ulna (point of elbow)
All heads are innervated by Radial nerve
NB: These groups of muscles are separated by intermuscular septum
