Background: Knee osteoarthritis is common in elderly people, and causes pain, loss of physical functioning, and disability. Elderly patients with knee osteoarthritis have relatively poor health-related quality of life, manifested mainly by pain. Aim: This study aimed to evaluate the effect of instructional guidelines on selected health outcomes among the elderly with knee osteoarthritis. Research Design: A quasi-experimental design was utilized to conduct the current study. Settings: This study was conducted at the rehabilitation units of three hospitals (Souad Kafafi University Hospital, Al Sheekh Zayeed Hospital and Central 6^th October Hospital). Subjects: A purposive sample of 80 patients diagnosed with knee osteoarthritis. Tools for data collection: Two tools were used for data collection. Tool I: A structured interview or self-administered questionnaire to assess patients' demographic data and health status; Tool II: Knee Injury and Osteoarthritis Outcome Score (KOOS) to assess patient-relevant outcomes following a knee injury. Results: This study revealed that; 43.7% of the study subjects were between 60 to <70 years with a mean age of 68 ± 1.367, and 60.2% were males. There was a highly statistically significant difference between patients' osteoarthritis outcome scores pre/post implementation of the instructional guidelines in all items except fully bending of the knee, going up or down stairs, knee stiffness after waking in the morning and ascending stairs. However, there was marked improvement post-implementation of the instructional guidelines. Conclusion: Designed and implemented instructional guidelines had a positive effect on improving selected health outcomes among the elderly with knee osteoarthritis Recommendation: Develop and apply similar instructional guidelines for studying more health outcomes among the elderly with knee osteoarthritis.