RESUMO
A second stage in the treatment of arthrosis following the non-steroid anti-inflammatories is formed by the so-called chondroprotectors and intraarticular viscosupplementation with hyaluronic acid, generally in the knee. Although infrequent, cases have been described of transitory inflammatory arthritis following intra-articulary administration. The main problem is differential diagnosis with a septic secondary arthritis and its consequences. This is a generally benign process with a still unknown transitory aetiology with different hypotheses, but which involves suspension of the treatment. We present two cases that resolved the sequels with different moments of appearance, the first in the three hours following infiltration, and the second four days later.