Snapshot A Introduction Clinical definition arthritis affecting a single joint there are various causes Epidemiology Risk factors prosthetic joint e.g., S. epidermidis Etiology Trauma Crystal-induced arthropathy (e.g., gout) Infection gonococcal nongonoccal S. aureus (most common) S. pneumoniae gram-negative bacteria Seronegative spondyloarthritis such as reactive arthritis psoriatic arthritis inflammatory bowel disease-associated arthritis Osteoarthritis Malignancy Presentation Symptoms pain that is worsened by movement of the joint decreases the range of motion of the joint not the case in deep-seated joints (e.g., shoulder and hip) is accompanied by swelling or erythema not the case in deep-seated joints (e.g., shoulder and hip) Physical exam A Imaging A Studies Arthrocentesis Synovial fluid analysis Differential A Treatment Medical Operative Evaluation Assume infected until proven otherwise. Radiograph shows joint space widening Arthrocentesis findings DiseaseFindingsGoutNegatively birefringent needle-shaped crystalsWBC < 50,000 mm3PseudogoutPositively birefringent rhomboid crystalsInfectionWBC > 50,000 mm3> 75% of neutrophilsLow glucoseArthritisWBC = 20,000 to 50,000 mm3 Treatment Antibiotics vancomycin + 3rd generation cephalosporin If gram positive and patient not at risk (not IVDU or immunocompetent) IV vancomycin If gram negative and patient not at risk (not IVDU or immunocompetent) 3rd generation cephalosporin (e.g. IV ceftriaxone) consider adding pseudomonas coverage for immunocompromised or at risk patients Complications A Prognosis dependent on the underlying cause of monoarthritis