BackgroundExercise is a recommended ‘core’ treatment for chronic knee pain (CKP), however it appears to be underused by general practitioners (GPs). While behavioural theories suggest that attitudes and beliefs influence behaviours, no single theory reliably predicts GPs’ behaviours. A theoretical analysis framework, developed from sociocognitive theories, was used to underpin investigation of the key influences associated with GPs’ use of exercise for patients with CKP, to inform future interventions to optimise GPs’ use of exercise.MethodsA cross-sectional postal questionnaire survey investigated UK GPs’ reported use of exercise based on a patient case vignette. Factors influencing GPs’ exercise use (behaviour) were examined using attitude statements, free-text questions and multiple response option questions related to factors within the analysis framework. Unadjusted logistic regression analyses explored the associations between GPs’ attitudes/beliefs and behaviour.ResultsFrom a total sample of 5000 GPs, 835 (17%) returned a questionnaire. Most respondents (n = 729, 87%) reported that they would use exercise. Factors significantly associated with exercise use (OR (95% CI)) included GPs’ beliefs about their role (belief that GPs should give information on type, duration and frequency of exercise (30.71 (5.02,188.01)), beliefs about consequences (agreement that knee problems are improved by local (3.23 (1.94,5.39)) and general exercise (2.63 (1.38,5.02))), moral norm (agreement that GPs should prescribe all patients local (3.08 (1.96,4.83)) and general exercise (2.63 (1.45,4.76))), and GP-related beliefs about capabilities (prior experience of insufficient expertise to give detailed exercise information (0.50 (0.33,0.76)). Whilst perceived time limitations were not associated with exercise use (1.00 (0.33,3.01)), GPs who disagreed that they experienced time limitations were more likely to suggest general (2.17 (1.04,4.55)), or demonstrate local (2.16 (1.06,4.42)), exercises.ConclusionGPs’ attitudes and beliefs are associated with their use of exercise for patients with CKP, particularly beliefs about role, responsibilities and skills in initiating exercise, and about the efficacy of exercise. Although the low response risks response bias, these results can inform future interventions to optimise GPs’ behaviour. The role of GP uncertainty and influences on clinical decision-making need further exploration, thus an amended analysis framework is suggested, which should be tested in future research.Electronic supplementary materialThe online version of this article (doi:10.1186/s12875-016-0570-4) contains supplementary material, which is available to authorized users.