Musculoskeletal: Upper Extremity: Acromioclavicular Joint: Osteokinematics and Arthrokinematics

Question 1

Acromioclavicular Joint:

Osteokinematic: Upward rotation of the Scapula

Answer 1

• The arthrokinematics of the AC joint during upward rotation of the scapula.
• With upward rotation of the scapula the concave surface of the AC joint rolls and glides SUPERIORLY on the convex surface of the AC joint due to the SUPERIOR movement of the bone. This occurs in conjunction with upward rotation of the scapula which occurs in conjunction with humeral elevation.

Question 2

Acromioclavicular Joint:

Osteokinematic: Downward rotation of the Scapula

Answer 2

• The arthrokinematics of the AC joint during downward rotation of the scapula.
• With downward rotation of the scapula the concave surface of the AC joint rolls and glides INFERIORLY on the convex surface of the AC joint due to the INFERIOR movement of the bone. This occurs in conjunction with downward rotation of the scapula which occurs in conjunction with downward movement of the humerus.

Question 3

Acromioclavicular Joint:

Osteokinematic: Protraction of the Scapula

Answer 3

• The arthrokinematics of the AC joint during protraction of the scapula.
• With protraction of the scapula the concave surface of the AC joint rolls and glides ANTERIORLY on the convex surface of the AC joint due to the ANTERIOR movement of the bone. This occurs in conjunction with protraction of the scapula which occurs in conjunction with protraction of the humerus.

Question 4

Acromioclavicular Joint:

Osteokinematic: Retraction of the Scapula

Answer 4

• The arthrokinematics of the AC joint during retraction of the scapula.
• With retraction of the scapula the concave surface of the AC joint rolls and glides POSTERIORLY on the convex surface of the AC joint due to the POSTERIOR movement of the bone. This occurs in conjunction with retraction of the scapula which occurs in conjunction with retraction of the humerus.