QuestionSBA
QuestionChoice
To prevent scapular winging, the serratus anterior (under the control of the long thoracic nerve) contracts, pulling the scapula anteriorly. Disruption of this nerve, for example by misplaced chest drain insertion, can cause scapular winging which can be corrected using a scapular brace.
10001068
c
When pushing the extended arm against a wall, a muscle contracts to keep the scapula in place
QuestionChoice
This is the locking of the knee. Upon full extension of the knee, the femur rotates inwards on the tibial plateau, causing the tightening of the anterior and posterior cruciate ligaments. This allows the leg to remain extended with less muscular activity to conserve energy while standing. This locking can then be unlocked by the popliteus muscle externally rotating the femur on the tibia.
10001067
b
Extension of the knee causes the leg to lock
QuestionChoice
When abducting the shoulder in the glenohumeral joint, the first 15 degrees of movement are mediated by the suprascapularis, and the next rotation up to 90 degrees is mediated by the deltoid. Further rotation from this point onwards is mediated by the rotation of the scapula at the acromioclavicular joint by the trapezius (as the glenohumeral joint is already at its full abduction).

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10001070
e
The rotation of the scapula during arm abduction
QuestionChoice
This is the windlass mechanism. Weight-bearing on the first metatarsophalangeal joint causes its extension, tightening the plantar aponeurosis into a tight band, raising the height of the medial longitudinal arch, externally rotating the leg, and inverting the calcaneus.
10001066
a
Pressure on the hallux causes tightening of the arch of the foot through the plantar fascia
QuestionChoice
The pelvis is formed of arches which produce strong structures for weight bearing. One arch is formed between the ischial tuberosities, pubis and pubic symphysis to support the body when sitting. Another is formed between the acetabulums, ilium and sacrum to support the body when standing.
10001069
d
When sitting, a bony arch supports the weight of the body
Concept
Chapter
2693
3877
Foot anatomy
Topic
145
Orthopaedics
12760
Which of these statements best describes the windlass mechanism?
a