Reactive arthritis is an inflammatory joint disease that develops after an infection and it usually occurs following a gastrointestinal or genitourinary system infection and it belongs to the family of arthritis called "spondyloarthritis." We wanted to represent a rare case of reactive arthritis secondary to Echinococcus infestation. Cyst hydatid disease is common in endemic regions like Turkey. Internal organ involvements, especially liver and lung, are most frequent involvements. Primary bone involvement is rare complication of Echinococcus infestation. In our case, the patient with Echinococcus infection developed right knee arthritis and sacroiliitis. Other reactive and oligoarthritis causes were excluded and diagnosis of reactive arthritis secondary to cyst hydatid infestation was done with the present findings. Cold pack and TENS treatment were applied as symptomatic treatment to the right knee of the patient. Acemetacin was given as medical treatment. On the 5th day of treatment, right knee and ankle arthritis were clinically regressed. In regions where the disease is seen as endemic, such as Turkey, patients with musculoskeletal symptoms should consider the possibility of musculoskeletal involvement due to the hydatid cyst.