The classic mechanism for nursemaids elbow is axial traction on a pronated forearm and extended elbow.
The force allows a portion of the annular ligament to slip over the radius.
Consider this diagnosis with other mechanisms of injury especially if the exam is not suggestive of fracture.
Suspect in a patient in minimal distress with arm held semi flexed and pronated.
A recent retrospective study looked at other mechanisms of injury.
69 subjects with a median age of 2.5 years
The most common mechanisms of injury were fall (57%), direct hit to the elbow (16%), and rolling over (7%).
Some studies note the left elbow is more commonly involved but this is likely due to most guardians being right-handed, thereby holding the child’s left hand
References
Li N, Khoo B, Brown L, Young T. Nonaxial Traction Mechanisms of Nursemaid's Elbow. Pediatr Emerg Care. 2021 Jun 1;37(6)
