This is a long-term research registry for patients with Achilles tendon disorders (like tears, chronic pain, or ruptures) as well as healthy adults without tendon problems. The goal is to collect detailed information over time to understand which treatments work best for different people, identify risk factors for injury, and improve overall care. Adults over 18, both with and without Achilles tendon conditions, are eligible to join. Participants will attend several assessment visits at the Prince of Wales Hospital over the first year (at the start, 6 weeks, 3, 4, 6, and 12 months) for physical tests, ultrasounds, and questionnaires. After the first year, follow-up continues with annual online questionnaires for up to five years. The main measure is a standard questionnaire about tendon pain and function (VISA-A). The study aims to use this information to guide better, more personalized rehabilitation strategies, improve patient outcomes, and reduce long-term disability. All participation is voluntary and requires written consent.