--- title: How is Reactive Arthritis Diagnosed? date: 2021-01-28T20:47:00-08:00 author: admin canonical_url: "https://marlerclark.com/foodborne-illnesses/reactive-arthritis/reiters-syndrome-symptoms-risks-1" section: Resource Library --- [Foodborne Illnesses](/foodborne-illnesses) / [Reactive Arthritis](https://marlerclark.com/foodborne-illnesses/reactive-arthritis) / # How is Reactive Arthritis Diagnosed? The American College of Rheumatology published diagnostic guidelines for ReA in 1999, citing three major criteria: 1. Characteristic findings on physical exam of the musculoskeletal system: asymmetrical oligo- or monoarthritis involving lower extremities. There may be enthesitis, dactylitis, or inflammatory back pain. 2. Evidence of a preexisting extra-articular infection, either enteritis or urethritis. This is usually a history of acute diarrhea (enteritis) or urethritis 3 days to 6 weeks prior to the onset of ReA symptoms. Sometimes there is a positive culture of the inciting organism, but not always, as the symptoms may develop after the acute infection has resolved. If there is still diarrhea, culture the stool for *Campylobacter*, *Salmonella*, *Shigella* and *Yersinia*. 3. No evidence for another cause of the arthritis. If there is fluid in the joint, it should be aspirated and cultured to exclude infection (septic arthritis). Other causes of arthritis include rheumatoid arthritis and crystal-induced arthritis, among others. Supporting laboratory tests can include elevated inflammatory markers in the blood, such as ESR and CRP. ![Inflamed synovial tissue](https://s3.us-west-2.amazonaws.com/aboutreactivearthritiscom-images/INFLAMED-SYNOVIAL-TISSUE-SHUTTERSTOCK-PURCHASED-PHOTO-4.28.21.jpg)Inflamed synovial tissue [ Next: What is the Prognosis for People Who Have Reactive Arthritis? › ](https://marlerclark.com/foodborne-illnesses/reactive-arthritis/reiters-syndrome-prognosis) ### More Information [August 13, 2026 ###### Cyclospora and the 2026 Taylor Farms Outbreak: Questions and Answers Marler Clark represents people sickened in the 2026 Cyclospora outbreak and has filed cases naming Taylor Farms entities as defendants. The answers below are written for people trying to understand ... ](https://marlerclark.com/news_events/cyclospora-and-the-2026-taylor-farms-outbreak-questions-and-answers) [August 13, 2026 ###### Salmonella and the 2026 Jalapeño Outbreak: Frequently Asked Questions Marler Clark — The Food Safety Law Firm | Updated August 13, 2026 The questions below come in two parts. The first covers Salmonella generally — what it does, how ... ](https://marlerclark.com/news_events/salmonella-and-the-2026-jalape%C3%B1o-outbreak-frequently-asked-questions) [August 08, 2026 ###### FAQ's: The 2026 Cyclospora Outbreak: Questions and Answers for the Public Updated Saturday, August 8, 2026. Everything below is drawn from the federal and state health department pages linked in the answers, and the numbers move, so check the links before ... ](https://marlerclark.com/news_events/faqs-the-2026-cyclospora-outbreak-questions-and-answers-for-the-public) [July 27, 2026 ###### The Cyclospora Lawsuits Have Begun On July 16, health officials linked shredded lettuce sold at US-based Taco Bell restaurants to the cyclosporiasis outbreak. Within hours, the lawsuits began. At least four lawsuits have been filed ... ](https://marlerclark.com/news_events/the-cyclospora-lawsuits-have-begun) [1. View all ](/news_events/outbreaks?illness=e-coli&year=all) ## All Reactive Arthritis Resources [###### What is Reactive Arthritis? ](https://marlerclark.com/foodborne-illnesses/reactive-arthritis/about-reactive-arthritis) [###### Symptoms of Reactive Arthritis ](https://marlerclark.com/foodborne-illnesses/reactive-arthritis/reiters-syndrome-symptoms-risks) [###### How is Reactive Arthritis Diagnosed? ](https://marlerclark.com/foodborne-illnesses/reactive-arthritis/reiters-syndrome-symptoms-risks-1) [###### What is the Prognosis for People Who Have Reactive Arthritis? ](https://marlerclark.com/foodborne-illnesses/reactive-arthritis/reiters-syndrome-prognosis) [###### Treatment for Reactive Arthritis ](https://marlerclark.com/foodborne-illnesses/reactive-arthritis/reiters-syndrome-treatment) [###### Can Reactive Arthritis be Prevented? ](https://marlerclark.com/foodborne-illnesses/reactive-arthritis/reiters-syndrome-prevention) [###### Reactive Arthritis References ](https://marlerclark.com/foodborne-illnesses/reactive-arthritis/reactive-arthritis-references) ### Other foodborne illnesses [E. coli](https://marlerclark.com/foodborne-illnesses/e-coli) [Salmonella](https://marlerclark.com/foodborne-illnesses/salmonella) [Listeria](https://marlerclark.com/foodborne-illnesses/listeria) [Hepatitis A](https://marlerclark.com/foodborne-illnesses/hepatitis-a) [Guillain-Barre Syndrome](https://marlerclark.com/foodborne-illnesses/guillain-barre-syndrome) [Irritable Bowel Syndrome](https://marlerclark.com/foodborne-illnesses/irritable-bowel-syndrome) [Norovirus](https://marlerclark.com/foodborne-illnesses/norovirus) [Botulism](https://marlerclark.com/foodborne-illnesses/botulism) [Campylobacter](https://marlerclark.com/foodborne-illnesses/campylobacter) [Shigella](https://marlerclark.com/foodborne-illnesses/shigella) [Cyclospora](https://marlerclark.com/foodborne-illnesses/cyclospora) [Hemolytic Uremic Syndrome](https://marlerclark.com/foodborne-illnesses/hemolytic-uremic-syndrome)