Chronic laxity of the subtalar joint derives from the functional significance of the joint with the talo-calcaneal interosseus ligament as articular "pivot". The subtalar joint has a determinant importance in the overall function of the foot and in the overall rotatory movements of the limb. The laxity of the subtalar joint is to be considered with traumatic or degenerative pathology of the talo-calcaneal interosseous ligament. Exceptionally when acute (microtraumatic) it is to be considered microtraumatic with degenerative aspects- frequently seen in sportsmen. The diagnosis is essentially anamuestic: minor distorsive episode after initial serious subluxation followed by the establishment of a sinus tarsi syndrome. The objective instability of the hindfoot in monopodal standing is significant as it excludes ankle pathology.The characteristic and elective pain is in relation to the sinus tarsi. On palpation at times, the tenderness is more proximal along the posterior subtalar joint. Roentgenographic examination is not significant. What is significant is the arthrographic obliteration of the normal synovial recess of the posterior subtalar joint corresponding to the sinus tarsi. Recently with the NMR it has been possible to document structural alterations of the talocalcaneal interosseous ligament in connection to one of acute or chronic traumatic pathology. The surgical reconstruction of the talo-calcaneal ligament is an operation in which the results with correct indication, are satisfactory by both Miralle's original tecnique and my techique. The results of 47 operations (44 patients of which 3 bilateral) performed in the period of January 1982-June 1992, has been discussed. Concluding, in a pathology still on the way to a definition, the reconstruction of the interosseous talo-calcaneal ligament could be considered a solution to a reasonable expectation of success on the condition that the indications, even in relation to the cartilaginous compromise, are well defined with the possibility of regeneration of the proprioceptive control.