Purpose Varus or valgus deformities in knee osteoarthritis may have a crucial impact on ankle subtalar range of motion (ROM) and ligamentous stability. The purpose of this study was to assess whether the grade of ankle eversion and inversion rotation stability was influenced by frontal deformities of the knee joint. Methods Patients who were planned to undergo total knee arthroplasty (TKA) were prospectively included in this study. Patients were examined radiologically (mechanical tibiofemoral angle (mTFA), hindfoot alignment view angle (HAVA), anterior distal tibia angle (ADTA)) and clinically (ROM of the knee and ankle joint, foot function index, knee osteoarthritis outcome score). Ankle stability was assessed using an ankle arthrometer (AA) to test inversion/eversion (ie) rotation and anterior/posterior (ap) displacement stability of the ankle joint. Correlations were calculated using Pearson’s coefficient, and differences between two independent groups of nonparametric data were calculated using a two-sided Wilcoxon signed rank test. Results Eighty-two (varus n = 52, valgus n = 30) patients were included. The preoperative mTFA significantly correlated with the HAVA (Pearson’s correlation = − 0.72, p < 0.001). Laxity testing of the ankle demonstrated that in both varus and valgus knee osteoarthritis, higher grades of mTFA did not correlate with the inversion or eversion capacity of the ankle joint. The ADTA significantly correlated with the posterior displacement of the ankle joint (cor = 0.24, p = 0.049). Conclusions This study could not confirm that higher degrees of frontal knee deformities in osteoarthritis were associated with increasing grades of ligamentous ankle instabilities or a reduced ROM of the subtalar joint. Level of evidence II.

Talar dislocations are rare injuries of the foot and ankle and require quick and decisive diagnostic and therapeutic decisions. Evidence concerning the treatment and outcome of these injuries is sparse. The aim of this study was to analyze all talar dislocations of the last ten years treated in a large German level I trauma center in an effort to add to the experience on these injuries. Methods: All patients with a talar dislocation injury were retrospectively included. Medical reports, x-ray and computertomography scans were analyzed for the sex, age, trauma mechanism, and injury classifications as well as for the clinical outcome as measured by the Foot Function Index (FFI). Results: A total of 18 patients were included in this study: Luxatio pedis cum talo (n ¼ 1), Luxatio tali totalis (n ¼ 3), Luxatio pedis sub talo (n ¼ 14). Analysis of the therapeutic algorithms revealed that only one patient was treated conservatively, the other 17 patients underwent operation. In most cases, stabilization was achieved using an external fixator and if necessary, the subtalar and talonavicular joints were temporarily stabilized using K-wires. The mean follow-up time was 4.25 years (2.05 SD) and the mean FFI-sum score 45.00 (42.26 SD). Two patients required subtalar fusion two years after the injury. Conclusion: Isolated talar dislocations can have a good outcome and be effectively treated in the emergency setting by basic techniqes if neurovasular structures are not injured. Often, these injuries are associated with fractures of adjacent bones which then need complex reconstruction.

Purpose The hindfoot is believed to compensate varus and valgus deformities of the knee by eversion and inversion movements. But these mechanisms were merely found in static radiologic measurements. The aim of this study was, therefore, to assess dynamic foot posture during gait using pressure-sensitive wireless insoles in patients with osteoarthritis of the knee and frontal knee deformities. Methods Patients with osteoarthritis of the knee were prospectively included in this study. Patients were clinically and radiologically (mechanical tibiofemoral angle (mTFA), hindfoot alignment view angle (HAVA), and talar tilt (TT)) exa mined. Gait line analysis was conducted using pressure-sensitive digital shoe insoles. Results Eighty-two patients (varus n = 52, valgus n = 30) were included in this prospective clinical study. Radiologically, the mTFA significantly correlated with the HAVA (cor = −0.72, p < 0.001) and with the TT (Pearson’s cor = 0.32, p < 0.006). Gait analysis revealed that the gait lines in varus knee osteoarthritis were lateralized, despite the hindfoot valgus. In valgus knee osteoarthritis, gait lines were medialized, although the hindfoot compensated by varization. Conclusions Functional dynamic gait analysis could demonstrate that the hindfoot is not able to sufficiently compensate for frontal malalignments of the knee joint, contrary to static radiologic findings. This led to a narrowing of the joint space of the ankle medially in varus and laterally in valgus knee osteoarthritis.