Background: The use of the Internet for seekers of health-related information provides convenience and accessibility to diverse sources (of variable quality) for many medical conditions. There is a suggestion that patients may find empowerment by engaging with Internet health care strategies and communities. The profile of consumers of online health information on knee pain has not been explored. Objective: Our objective was to identify the characteristics and motivations of online health information-seekers accessing the online health community, KNEEguru (KG). The study was designed to obtain the respondents' sociodemographic profile, together with their main reasons and motivations for joining such a community, their health information-seeking behavior, the extent of their knee problems, and their general Internet usage. Methods: We undertook an online questionnaire survey, offered to users of the KG website from June to July 2012. A mix of open and closed questions was used to facilitate inductive enquiry. Quantitative responses were analyzed using univariate analysis; qualitative thematic analysis of the open responses was completed and a conceptual model was developed. Results: One-hundred and fifty-two respondents took part (11.56% response rate, 152/1315), with a mean age of 40.1 years. Of this cohort, 61.2% were female, 68.4% were in domestic partnerships, 57.2% were employed, 75.0% had higher education qualifications, and 80.3% were of white/Caucasian ethnicity. Females were associated with joining KG in order to get emotional support from other users (OR 2.11, 95% CI 1.04 - 4.27, P=.04). Respondents' self-perception of health was associated with reported quality of life (OR 10.86, 95% CI 3.85 - 30.43, P<.001). Facebook users were associated with joining KG to share experiences (OR 2.34, 95% CI 1.04 - 5.56, P=.03). Post-surgery respondents were associated with joining KG to compare symptoms with other users (OR 7.31, 95% CI 2.06 - 39.82, P<.001). Three key themes were induced: condition, emotion and support. Respondents expressed distress and frustration at uncertainty of prognosis around various knee conditions, with some users preferring to initially observe rather than engage. Conversely, a strong desire to inform and support other community members was stated with reciprocation of ideas and experiences. KG was conceptualized as a filter that takes an individual's condition and emotional response to that condition as basis for support; this filter facilitated validation as the outcome of engagement. Conclusions: This study, in line with wider literature, suggests that users of an online knee-specific community are typically female, middle-aged, white/Caucasian, married, employed, and have attained a level of higher education. These users demonstrate a pragmatic approach to health care information with altruistic motivations and a desire to share experiences as a means of validation. This finding emphasizes a means of promoting efficient and appropriate online health care, and demonstrates the benefits of the Internet as a viable complement to clinical engagement.