[Sinus tarsi syndrome: what hurts?].

Sinus tarsi syndrome, described by O'Connor in 1958 and Brown in 1960, is a clinical finding often seen after an accident, consisting of a painful reaction to pressure on the sinus tarsi. This syndrome has also been described in dancers, volleyball and basketball players, overweight individuals, and patients with foot deformities (flatfoot). We looked for mechanical and functional macroscopic structures in the canalis and sinus tarsi that can be associated with sinus tarsi syndrome in order to deduce therapeutic consequences. We found a complex fibrous layer in the sinus and canalis tarsi that forms slips around the synovial sheats of the extensor tendons under the inferior extensor retinaculum. Both limbs run deep to the base of the sinus and canalis tarsi. The lateral band inserts into the sinus tarsi at the calcaneus, while the medial band inserts at the canalis tarsi at the talus and calcaneus. Instead of the term "interosseous ligaments," we recommend referring to the "fundiform ligament" with one lateral and one medial band. Regarding function, one can assume that the medial band of these fundiform ligaments controls the talus at eversion and inversion together with the well-vasculated and well-innervated interarticular fat pads in the sinus and canalis tarsi. While contracting the long extensor muscles of the toes, the ligament forms a control mechanism for the longitudinal arch of the foot in the moving phase.A question is how variations in vascularization or disorders in innervation will alter the turgor of the pads of fat tissue. That is, such alterations would influence the distribution of synovia in the neighboring joints as well as the tension of the involved ligaments.