BACKGROUND: Tibial shaft fractures require surgical stabilization preferably by intramedullary nailing. Recovery is often unsatisfactory due to limited knee function and pain, resulting in reduced quality of life. The extent of these functional limitations with respect to gait deficits has not been sufficiently recognized. RESEARCH QUESTION: Are there functional limitations during gait and squat performance during the first six months after surgically treated tibial shaft fractures? METHODS: Twenty-three patients (BMI: 24 ± 3, Age:39 ± 15) with tibial shaft fractures and 23 healthy, matched controls (BMI: 24 ± 3, Age: 40 ± 14) were assessed using instrumented motion analysis two, three and six months after surgery. Kinematic and kinetic data of the lower extremities were collected during level walking and squat performance. Data were compared among follow-up time intervals and between groups. RESULTS: Significant improvements were found for all spatiotemporal parameters and most kinetic parameters. Even six months after surgery functional deficits persisted when compared to healthy controls. There were only slight improvements in sagittal knee and ankle kinematics as well as knee moments and power within the follow-up period. A significant difference compared to the healthy controls can still be observed in these parameters. SIGNIFICANCE: Although patients with tibia fractures demonstrated functional improvements over the early course of healing, some residual deficits in lower extremity movement biomechanics were identified at six months post surgery. In particular knee kinematics in squatting as well as knee kinematics and kinetics during walking only recovered incompletely. This result can help explain the often-reported functional limitations. CLINICAL TRIAL REGISTRATION NUMBER: German register for clinical trials (DRKS00023790).