The aim of this systematic review was to examine the effects of foot orthoses on gait kinematics and low back pain (LBP) in individuals with leg length inequality (LLI). This review was conducted in accordance with the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines and has been undertaken in the PubMed-NCBI, EBSCO Host, Cochrane Library, and ScienceDirect databases. Inclusion criteria were the analysis of kinematic parameters during walking or LBP before and after foot orthosis use in patients with LLI. Ultimately, five studies were retained. We extracted the following information: study identity, patients, type of foot orthosis, duration of orthopedic treatment, protocols, methods, and data to assess gait kinematics and LBP. The results showed that insoles seem to reduce pelvic drop and active compensations of the spine when LLI is moderate/severe. However, insoles do not always seem to be efficient in improving gait kinematics in patients with low LLI. All of the studies noted a significant reduction of LBP with use of insoles. Consequently, although these studies revealed no consensus on whether and how insoles affect gait kinematics, the orthoses seemed helpful in relieving LBP.