Joints
Acromioclavicular joint
The connection between the lateral end of the clavicle and the acromion. It does not move on its own but follows the scapula: without this joint the shoulder blade cannot rotate around the rib cage.
- Joint type
- Plane joint (art. plana) with a disc, three degrees of freedom with small excursion
- Body region
- Shoulder
- Latin name
- Articulatio acromioclavicularis
Movements, axes and normal values
| Movement | Plane | Axis | Normal range | End feel |
|---|---|---|---|---|
| Rotation of the clavicle | along the long axis | longitudinal (clavicle) | 20-30 degrees during full arm elevation | elastic |
| Scapular tilt and rotation | compound | variable | small translations, not measurable separately | elastic |
- Close-packed position
- 90 degrees of arm abduction
- Resting (loose-packed) position
- Arm by the side
- Capsular pattern
- Pain at the end of range in every movement, most clearly on horizontal adduction
- Arthrokinematics
- Two nearly flat joint surfaces that mainly glide and tilt; the coracoclavicular ligament (conoid and trapezoid parts) couples the rotation of the clavicle to the position of the scapula.
- Stability
- Capsule and acromioclavicular ligament against horizontal displacement, coracoclavicular ligament against vertical displacement.
- Palpation
- The joint line lies about a finger's width medial to the lateral border of the acromion; follow the clavicle laterally until you feel the step.
- Clinical
- AC dislocation after a fall onto the shoulder, graded by Tossy or Rockwood; osteoarthritis of the joint causes pain high in the arc and on cross-body adduction.
- Source
- Kapandji, Physiologie articulaire deel 1; Magee, Orthopedic Physical Assessment