A crioterapia melhora a função da marcha e reduz a inflamação sinovial de ratos com osteoartrite do joelho induzida por transecção do ligamento cruzado anterior

Abstract

Knee osteoarthritis (KOA), the most frequent degenerative articular disorder in adults and seniors, is considered one of the primary causes of pain and functional disability. Animal models of post-traumatic KOA, such as anterior cruciate ligament transection (ACLT), have been widely used because of their similarity to KOA in humans. Through these models, one can test the effect of physical therapy interventions, such as cryotherapy, as well as characterize aspects related to the pathogenesis of KOA. In this sense, the objectives of this thesis were: 1) to evaluate the effects of clinical-like cryotherapy on gait function and synovial inflammation in rats with KOA induced by ACLT; 2) To compare the unilateral signs of knee osteoarthritis (KOA) 30 and 60 days after anterior cruciate ligament transection (ACLT). Pain, gait function, synovial fluid inflammation and histopathological changes in the synovial membrane were analyzed, as well as the interaction between the variables. For this, 64 male Wistar rats (Rattus norvegicus) were divided in two studies. In the first study, 32 rats were randomly divided into four groups of 8 animals each: KOA (ACLT knee surgery), KOA+Cryotherapy (ACLT knee surgery and ice pack) and KOA+Placebo (ACLT knee surgery and sand pack). Sixty days after surgery, both the KOA+Cryotherapy and KOA+Placebo groups received their respective interventions twice a day, for 20 min each, over five consecutive days (from the 61st to 65th days). Gait test, skin temperature, thermal response threshold and joint swelling were assessed in all groups before ACLT surgery, and pre (60th day) and post (66th day) intervention protocols. Synovial fluid (account of leukocytes and cytokine levels) and synovial membrane (histopathological analysis) were collected on the 66th day. It was concluded that clinical-like cryotherapy improves the gait function and reduces the number of leukocytes and inflammatory cytokines in synovial fluid of rats with ACLT-induced KOA. These results suggest that it can be used as a non-pharmacological and complementary treatment to control joint inflammation in the chronic phase of KOA. In the secondy study, 32 male Wistar rats were randomly distributed into four groups of 8 animals each. Two control groups (without surgery) were also assessed after the same time periods (C30 and C60). All the groups were evaluated before ACLT from the least to most stressful tests (skin temperature, mechanical response threshold, gait test, thermal response threshold and joint swelling), as well as 30 and 60 days after surgery. After euthanasia, the synovial fluid and synovial membrane were collected. It was concluded that 30 days after ACLT is sufficient to induce all KOA signs in rats, suggesting that a shorter period of time can be used as an experimental model.