Reactive arthritis (ReA) is sterile synovitis secondary to infection elsewhere in the body. Classic reactive arthritis is a subtype of spondyloarthritis which occurs secondary to enteric or urogenital infections. Organisms commonly associated with ReA  are Chlamydia trachomatis, Shigella flexneri, Salmonella enteritidis, Campylobacter jejuni, Clostridium difficile, and Ureaplasma urelyticu, Escherichia coli, Borrelia burgdorferi . Urethritis, conjunctivitis and oligoarticular lower limb joint involvement may occur. HLA-B27 allele is strongly associated with the development of ReA. Clinical manifestations include   asymmetric,   additive ,oligoarticular (2-4) lower limb joint involvement, inflammatory low backache and enthesitis, uveitis and conjunctivitis may occur. Hyperkeratosis of palms and soles ( Keratoderma blenorrhagica) , mucocutaneous lesions in the oral cavity and genitalia and nail dystrophy may also be seen. Cardiac conduction abnormalities in early disease and aortic insufficiency in late disease are rare manifestations.

ReA may also occur secondary to tubercular infection (Poncet’s disease). It is rare acute or subacute, oligo or polyarticular synovitis secondary to active tubercular infection elsewhere in the body. Large or small joints may be involved.  Arthritis resolves with antitubercular treatment within few weeks.  No sacroiliitis or joint destruction has been seen. It is a diagnosis of exclusion so synovial,  fluid analysis and biopsy should be done to exclude tubercular infection of the joint.

Rheumatic fever (RF) and joint involvement is a well known entity, occurs 2-3 weeks after  beta hemolytic streptococcal pharyngeal infection and is migratory, involving large joints and is self limiting but may recur with subsequent streptococcal infections. Major and minor revised Jones criteria are there to diagnose RF. while post streptococcal ReA has also been described which is different  from Rheumatic fever as this is non-migratory, additive, polyarthritis (involving small and large joints) which is not responsive to acetyl salicylic acid and occurs 7-10 days after streptococcal infection and may persist for 2 months or more and is recurrent.