instruction: what is the number of patients whose diagnoses short title is enthesopathy of hip and lab test fluid is joint fluid?
response: SELECT COUNT(DISTINCT demographic.subject_id) FROM demographic INNER JOIN diagnoses ON demographic.hadm_id = diagnoses.hadm_id INNER JOIN lab ON demographic.hadm_id = lab.hadm_id WHERE diagnoses.short_title = "Enthesopathy of hip" AND lab.fluid = "Joint Fluid"