Swimming training imposes a considerable stress about the joint and musculoskeletal structures. This study aimed to identify the postural changes and joint instabilities of federated Brazilian swimming. The authors evaluated 60 swimmers, 29 (48%) women and 31 (52%) men, with an average age of 20±3 years. To appraise the joint instabilities, the authors performed the drawer tests on anterior and posterior shoulder, sulcus test, drawer test anterior and posterior knee, stress test abduction (valgus) and stress test adduction (varus). Statistical analysis used SAS V.9 software and the exact Fisher's test. The main swimming styles were crawl (42%) and butterfly stroke (25%) and the practice time was 9±4 years. In women, the main alterations were: hyperkyphosis chest and knee hyperextension (66%), rotation of left shoulder girdle (52%), convex right scoliosis (45%). In men: hyperkyphosis chest (71%), knee hyperextension (68%) and low back pain (58%). The authors verified an association between the genres and alterations in lumbar spine (p=0.01), that 12 women had convex right scoliosis and 22 men did not have. The authors did not observe an association between the genres in relation with joint instabilities, but the women showed instability in the shoulders (76%), and the men laxity of the lateral collateral ligament (74%) and instability in the shoulders (61%). The overload of this sport is more visible in the region of the shoulder, area of more frequency of lesions found in this work, requiring intensive programmes of prevention and accompaniment of these athletes of swimming competition.