Objective <p>The aim was to compare the image quality of photon-counting detector CT (PCD-CT) and energy-integrating detector CT (EID-CT) in patients with tibial plateau fractures treated with metallic osteosynthesis material, and to identify optimal reconstruction parameters for PCD-CT.</p> Materials and methods <p>After ethical approval, twelve patients underwent PCD-CT and EID-CT scans. Images were reconstructed using bone and soft-tissue kernels with metal artifact reduction (iMAR). PCD-CT virtual monoenergetic images (VMI) at 70, 110, and 150 keV were generated. Five radiologists assessed metal artifact severity and bone and soft-tissue visualization using a 7-point Likert scale. Visual grading characteristics analysis was performed. Noise levels were quantified and compared using Wilcoxon’s signed-rank test.</p> Results <p>EID-CT was rated superior in reducing metal-artifact streaks (AUC: 0.10–0.21). No significant difference was found between EID-CT iMAR and PCD-CT VMI at 110 keV and 150 keV (AUC: 0.40–0.49) concerning the metal-bone interface. An ultra-high-resolution PCD-CT kernel outperformed its EID-CT counterpart in bone visualization, with AUC values of 0.67–0.92 across all bone criteria, including those incorporating artifact-affected regions. PCD-CT showed lower noise.</p> Conclusion <p>Metal artifact reduction was superior in EID-CT iMAR images compared to PCD-CT iMAR and VMI 110/150 keV, except at the metal-bone interface, where EID-CT iMAR images and PCD-CT VMI 110/150 keV performed comparably. The ultra-high-resolution PCD-CT kernel provided the best bone visualization, even when artifact-affected areas were included. Noise levels were lower in PCD-CT. This is the first <i>in vivo</i> comparison of photon-counting and energy-integrating CT for postoperative knee imaging with metallic osteosynthesis material.</p> Relevance statement <p>These findings highlight the need for improved metal artifact reduction in PCD‑CT, while demonstrating superior bone visualization, and support a complementary interpretation strategy in postoperative knees using high‑energy VMI and MAR‑corrected reconstructions.</p> Key points <p><UnorderedList Mark="Bullet"> <ItemContent> <p>Photon-counting CT demonstrated excellent bone visualization.</p> </ItemContent> <ItemContent> <p>Conventional EID-CT achieved better metal artifact reduction than photon-counting CT.</p> </ItemContent> <ItemContent> <p>The metal-bone interface was rated similarly for energy-integrating CT and photon-counting CT virtual monoenergetic images.</p> </ItemContent> <ItemContent> <p>These findings indicate that further improvements in metal artifact reduction algorithms for PCD-CT are warranted.</p> </ItemContent> </UnorderedList></p> Graphical Abstract <p></p>