This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Upper Limb Traumatology, Subject name: Orthopaedics
Which of the following is test of posterior glenohumeral instability: 
Select and explain. 
A. Fulcrum test, B. Sulcus test, C. Jerk test, D. Crank test
C: Jerk test
Answer: C: Jerk test 
Explanation: Posterior Instability (Adduction and internal rotation force) Jerk (provocative) test Posterior apprehension test Posterior clunk test Push-Pull test Anterior Instability Tests Fulcrum test Crank test Surprise test (most accurate) Jobe relocation test