This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous, Subject name: Orthopaedics
Which of the following is not a component of Kocher's criteria when diagnosing septic arthritis of the hip? 
Select and explain. 
A. Non-weight-bearing on the affected side., B. Erythrocyte sedimentation rate (ESR) greater than 40mm/hr., C. White blood cell (WBC) count of >12000mm3., D. C-reactive protein (CRP)>20.
D: C-reactive protein (CRP)>20.
Answer: D: C-reactive protein (CRP)>20. 
Explanation: Ans. D. C-reactive protein (CRP) >20.Due to the rapid chondro lytic effect of pus within the joint, pyogenic septic arthritis of the hip in children represents a surgical emergency. It can be difficult to distinguish a septic hip from other causes of hip pain in children. In such cases, whilst clinical suspicion remains of paramount importance, Kocher's diagnostic algorithm is a useful tool. The four diagnostic criteria are non-weight-bearing, ESR >40, WBC >12 and fever. The predicted risk of a septic arthritis varies with the number of positive criteria. The algorithm has been tested retrospectively and prospectively. In the prospective validation study the probabilities were lower:Number of criteria metChance of septic arthritis (original study)Chance of septic arthritis (validation study)13%9.5%240%35%393%73%499.6%93%