Suspected septic arthritis r/foot swollen red sore pus discharge but bloods show normal crp and wcc. still possible? uss says yes but doc not sure

Unusual: That is unusual. The crp is a very sensitive test for inflammation and usually would be extremely elevated in an infection. Ultimately, if the answer is not clear and a septic joint is a concern, an aspiration of the joint and doing a cell count from the fluid is the gold standard in making the decision whether a joint is or is not septic. The fluid can also be checked for crystals as in gout.