Purpose: Achilles tendon rupture is a common injury in ageing and sporting populations. The Thompson test has historically been utilised for diagnosis with high sensitivity. Contemporarily, ultrasound sonography (USS) is frequently used to confirm diagnosis. USS is operator dependent, incurs additional cost, and has variable reliability. The incremental benefit of USS over structured clinical examination therefore remains uncertain. This study aimed to determine whether the Thompson test is non-inferior to USS in identifying Achilles tendon ruptures requiring operative management. Methodology: A retrospective audit was conducted at a tertiary orthopaedic centre between 2017 and 2025. Adult patients presenting with suspected Achilles tendon rupture were included. Patients were excluded if definitive intraoperative diagnosis was unavailable. Demographic characteristics, mechanism of injury, Thompson test findings, USS reports, management, and intraoperative findings were recorded. Intraoperative findings were used as the gold standard for rupture classification. Results: A total of 101 patients were identified (77 males; 24 females), with mean age of 39 years. Six injuries occurred in professional athletes. Sixty-one patients had USS and rupture severity confirmed intraoperatively. Within this cohort, USS demonstrated a sensitivity of 0.87 and a positive predictive value (PPV) of 0.98 for identifying complete rupture. The Thompson test demonstrated a higher sensitivity of 0.93 with an equivalent PPV of 0.98. Conclusion: The Thompson test was non-inferior and superior to USS in identifying Achilles tendon rupture requiring operative intervention. These findings emphasise clinical examination and suggest USS may be avoided in clinically evident cases, saving costs and expediting definitive care. Future work should develop a clinical decision tool incorporating age, mechanism of injury, and Thompson test findings to guide management of suspected Achilles tendon rupture.