Cyberchondria may be defined as heightened distress evoked through excessive searches of the internet for medical information. In healthy people, cyberchondria is associated with a greater intolerance of uncertainty and greater health anxiety. These relationships are likely bidirectional. People who have a greater intolerance of uncertainty may be more likely to search the internet for medical information and have greater health anxiety. This greater health anxiety may lead to an increased likelihood of engaging in further internet searches and greater intolerance of uncertainty. These three constructs are important for patients because they impact patient function and health care costs. We were specifically interested in understanding the role of cyberchondria in the association between intolerance of uncertainty and health anxiety among orthopaedic patients because it has not been explored before and because knowledge about these interactions could inform treatment recommendations. Does cyberchondria mediate (that is, explain) the association between intolerance of uncertainty and health anxiety in orthopaedic patients searching for medical information on the internet, after controlling for potentially confounding variables? This was a cross-sectional study of 104 patients who had searched the internet for any medical information about their current condition. A research assistant approached 155 patients attending two orthopaedic outpatient clinics, one hand and upper extremity service and one sports medicine clinic, during a 3-month period. Ten patients declined to participate and 41 patients were excluded, predominantly because they had never searched for medical information online. The patients completed the Cyberchondria Severity Scale, Intolerance of Uncertainty Scale-short version, Short Health Anxiety Inventory, and a numerical rating scale for pain intensity at baseline, as well as demographic and clinical questionnaires. We performed a series of linear regression analyses to determine whether a greater intolerance of uncertainty predicts greater cyberchondria (mediator) and whether cyberchondria predicts greater health anxiety. Although it is more appropriate to use the language of association (such as "whether cyberchondria is associated with health anxiety") in many observational studies, here, we opted to use the language of causation because this is the conventional language for studies testing statistical mediation. After controlling for potentially confounding variables including pain intensity, multiple pain conditions, and education, cyberchondria explained 33% of the variance of the effect of intolerance of uncertainty on health anxiety (95% CI, 6.98 to 114.72%; p < 0.001). Among orthopaedic patients who search the internet for medical information, a greater intolerance of uncertainty is associated with greater cyberchondria, which is associated with greater anxiety about health. Identifying patients with an intolerance of uncertainty and educating them about the negative role of compulsive searches for medical information may improve the success of orthopaedic treatment. Orthopaedic surgeons should also consider making referrals for cognitive behavioral therapy in these instances to increase the patient's tolerance of uncertainty, decrease internet searching habits, and reduce anxiety about health. Level III, prognostic study.