<prompt> Most commonly affected joint in syphilis:AnkleKneeHipElbow  <response>: Ans. b Knee joint. Ref. Maheshwari, Orthopaedics, 2nd ed., 165CONGENITAL SYPHILIS Most commonly affected joint in syphilis knee joint. Syphilis may affect joints in following stages. Early: During infancy, osteochondritis in the juxta epiphyseal region results in breakdown of bone cartilage. Late: A manifestation of congenital syphilis, CLUTTONS JOINTS is a painless synovitis occurring at puberty most commonly affecting knee elbow mostly bilateral. DiseaseThe most commonly affected joint1TBSpine2Cong SyphilisKnee3PyogenicHip4OsteoarthritisKnee5RAIP6CharcotsAnkle7DiabetesIntertarsal8Recurrent DislocationShoulder9SyringomyeliaShoulder10GoutFirst metatarso-phalangeal11PseudogoutKnee 