[Biomechanics of the arch of the foot. Pre- and postoperative radiological examination].

The human foot is a complex biomechanical structure. The arch of the foot is formed by the bony and articular structure of the midfoot and supported by strong ligaments and tendons. The normal arch develops in childhood. Tendon and ligament rupture and degeneration often lead to flattening of the arch. Frequent painful conditions include hallux valgus deformity and rupture of the posterior tibial tendon both leading to flat feet. Radiological examination is necessary in a standardized, full weight bearing standing position. The standing dorsoplantar view shows hallux valgus angle and intermetatarsal 1/2 angle. The side view shows Lisfranc joint instability and decrease of the talometatarsal angle. Talonavicular instability is a frequent secondary sign of spring ligament and posterior tibial tendon lesion. After failure of conservative therapy, corrective surgery with osteotomy and realignment procedure of the malpositioned bones in combination with tendon and ligament reconstruction is the state of the art procedure. In postoperative follow-up a standing X-ray of the foot is again the standard tool. Additional MRI and CT examinations help to detect bone and cartilage lesions and tendon/ligament ruptures.