MST 2 - upper limb joints Flashcards
Joint stability and mobility are at the opposite ends of a continuum. What gives joints mobility/stability? Give examples.
Stable joints have congruent and often deep articular surfaces. They have a tight capsule with strong ligaments.
Mobile joints have a greater range of movement, for example, ball and socket joints. They often rely on fixator muscles for stability, and are susceptible to subluxation or dislocation due to their instability.
Name the joints of the shoulder complex.
The joints of the clavicle; sternoclavicular joint and the acromioclavicuar joint, as wel as the glenohumeral joint and the scapulo-thoracic joint.
Between which two bones is the sternoclavicular joint? What movements are allowed by this joint? What type of joint it is? List its main features.
The sternum and the clavicle, in the midline of the chest. Only point of articulation between the upper limb and the axial skeleton. It allows rotation, elevation and depression, and retraction and protraction. It is a saddle type synovial joint. The intra-articular disc in this join gives more mobility. It has a very strong capsule and is reinforced by the costoclavicular ligament.
Between which two bones is the acromioclavicluar joint? List its main features.
Between the clavicle and the scapula. It is a plane synovial joint, with a weak capsule, reinforced by the coracoclavicular ligament. It is susceptible in contact sports.
What is the correct name of the joint commonly thought of as the shoulder?
Glenohumeral joint
What type of joint is the glenohumeral joint?
A ball and socket joint. The glenoid fossa is shallow, the humerus head is large, and so the joint is very unstable.
How is the glenohumeral joint deepened?
By the glenoid labrum
What structures support the glenohumeral joint?
The coracoacromial ligament above (stops superior dislocation), the long head of biceps infront (prevents anterior dislocation) and the rotator cuff muscles above, behind and infront.
How many rotator cuff muscles are there? Name them.
- Supraspinatous, infraspinatous, teres minor and subscapularis. Their tendons blend with the joint capsule so that the contraction of these muscles tightens the capsule, pulls the humerus head towards the glenoid and makes the joint more stable.
Where is the subacromial bursa located? During what movement is it most likely to produce pain if inflamed?
Beneath the acromion process of the scapula. During shoulder abduction, particularly if the thumb is pointed down, resulting in a 60 degree painful arc of movement.
Force applied to an abducted and externally rotated arm is most likely to result in what type of shoulder dislocation?
Anterior dislocation. This is the most common type of dislocation.
Falling forward onto an outstretched arm is most likely to result in what type of shoulder dislocation?
Posterior. This is less common
A teared glenoid labrum increases the risk of what kind of clinical injury?
Shoulder dislocation.
During a shoulder dislocation, how does the humerus move relative to the glenoid fossa, and what structures are at increased risk?
The humerus drops inferiorly, and the nerves are at increased risk of injury.
Is the scapulothoracic joint a true joint or a physiological joint?
A physiological joint between the scapula and the thoracic cage.
What does scapulo-humeral rhythm refer to?
The way in which the scapulo-thoracic joint movement can work together with glenohumeral movement to allow greater abduction of the arm. The scapula can rotate 60 degrees, while the humerus lifts 120 degrees, to result in 180 degrees of abduction.
