RS full form in medical term is Reactive arthritis which is a very rare condition. The actual causes of reactive arthritis are still unknown, but it is associated with sexually transmitted infections and gastroenteritis. In simple language, Reactive Arthritis is a response of the human immune system against gram-negative bacteria such as Chlamydia, Salmonella, Yersinia, E.Coli, etc. A patient usually shows the symptoms after 2 to 3 weeks of infection from such bacteria, since the immune system takes time to kick in and respond against the bacterial invasion.
In most cases, when the initial infection begins, it affects large joints in the human body. And because of that, the patient feels lower mobility in the joint, swelling, and excruciating pain in that area. This infection can also affect other parts of the body such as the lining of the urethra and conjunctiva. And when all three body parts (joint spaces, urethra lining, and conjunctiva) are affected by the infection, it’s called Reiter’s Syndrome. But Reiter Syndrome is pretty uncommon because in most cases, the infections stay limited to the joint spaces and can be treated with highly effective antibiotics, and anti-inflammatory medications.