Understanding and mitigating high-order non-linearities is essential for ensuring long-term beam storage in high-energy colliders. The stability of particles at the Large Hadron Collider (LHC) is indeed strongly influenced by non-linear effects, particularly at injection energy where the beam occupies a large fraction of the vacuum chamber. Among these effects, third-order chromaticity, primarily driven by decapolar fields, limits dynamic aperture and beam lifetime. Despite corrections based on magnetic measurements and model predictions, a discrepancy remains between the measured and expected third-order chromaticity, indicating the presence of residual decapolar components. In this study, the decapolar fields in the LHC at injection energy are investigated and their impact on beam dynamics assessed. Chromatic amplitude detuning and decapolar Resonance Driving Terms (RDTs) are directly measured for the first time, using forced oscillations driven by an AC-Dipole. These measurements provide new insights into the source and impact of decapolar fields in the LHC and indicate that refined correction strategies could enhance beam lifetime, particularly for high-brightness operation in future runs.