Adherence to home-based musculoskeletal physiotherapy is less than optimal, which may lead to poor treatment outcomes. Physiotherapy adjuncts that increase patients’ self-efficacy and understanding of treatment facilitate rehabilitation adherence. The Health Action Process Approach (HAPA) that includes action and coping plans strengthens self-efficacy, while computer based patient education (CBPE) enhances patient understanding of treatment requirements when underpinned by the Cognitive Theory of Multimedia Learning. This thesis evaluated the effect of CBPE developed using the Cognitive Theory of Multimedia Learning and delivered in conjunction with action and coping plans on patient adherence to physiotherapy for shoulder injuries/disorders; and the value of extending the HAPA to include functional outcomes. The CBPE content was displayed using animations, videos, written text, and graphics, and included interviews with a physiotherapist and patient, exercise demonstrations, adherence hints, activities of daily living, information about the shoulder anatomy and pathologies, frequently asked questions and quizzes. A four week one group prospective pilot study (n = 20) assessed the effect of CBPE combined with action and coping planning on adherence to physiotherapy, the procedures for the main study, and the feasibility of extending the HAPA to include functional outcomes. After their first physiotherapy appointment participants completed questionnaires measuring the HAPA motivational variables (risk perception, outcome expectancies, action self-efficacy and behavioural intentions), shoulder knowledge and functional outcomes, and made action and coping plans. Throughout the study clinic- and home-based adherence were measured, and at the end participants completed questionnaires evaluating the HAPA volitional variables (maintenance and recovery self-efficacy, and adherence), knowledge and shoulder function. The HAPA variable scores were high with moderate to strong correlations between the behavioural intentions and self-efficacies, behavioural intentions and adherence behaviours, and adherence behaviours and post-study shoulder function. Participants’ shoulder function improved significantly during the study, and they valued the CBPE. The extended HAPA model incorporating functional outcomes was supported. The findings and feedback from the participants and physiotherapists led to changes to the CBPE programme, which included strategies to boost self-efficacy, less exercises, simpler terminology, diary page changes and increasing the Likert scale to 7 points for HAPA variables. The main study (n = 108) was an eight week two group randomised controlled trial, in which participants were allocated to either the combined CBPE planning group or the attention control group. This study tested the effect of the combination of CBPE and planning on rehabilitation adherence and shoulder function, evaluated the extended HAPA model, and validated the three-factor Rehabilitation Adherence Measure for Athletic Training (RAdMAT) as a measure of clinic-based adherence. The variables and their measurement timing were the same as the pilot study. The combined CBPE planning group had significantly higher levels of clinic-based adherence than the control and were highly satisfied with the programme. Moderately strong significant correlations occurred amongst all motivational stage HAPA variables, the three self-efficacies and behavioural intentions, the volitional self-efficacies and home-based adherence, clinic-based adherence and behavioural intentions, and clinic-based adherence and maintenance self-efficacy. Self-efficacy was the strongest predictor of behavioural intentions and home-based adherence. Significant moderately strong correlations existed between the RAdMAT and clinic- and home-based adherence measures. This thesis’ key findings are combining the CBPE programme underpinned by the Cognitive Theory of Multimedia Learning with action and coping plans enhances adherence; self-efficacy is associated with home-based adherence; relationships exist between adherence and functional outcomes; the HAPA can be extended to include functional outcomes; and the RAdMAT is a valid measure of clinic-based adherence.