BACKGROUND: Readability is a vital component of health information and providing this material at an appropriate literacy level may positively influence patient experience. OBJECTIVE: To assess the readability of the information provided within total hip replacement and total knee replacement apps to understand more about the impact this could have on patients. METHOD: A systematic search was conducted across the 5 most popular smartphone app stores: iTunes, Google Play, Windows Mobile, Blackberry App World, and Nokia Ovi. Apps were identified for screening if they: targeted total hip replacement or total knee replacement patients; were free of charge; and were in English. App readability assessment was conducted independently by 3 reviewers using the Gunning Fog Index, the Flesch Reading Ease Score, and the Flesch-Kincaid Grade Level. RESULTS: Fifteen apps met the inclusion criteria. Only one app was found "easy to read" (My THR). CONCLUSION: Findings suggest that the overall readability of information provided is written at a level which is difficult for patients to comprehend. App developers should engage patients in the design process of their apps, in order to enhance patient experience and for the potential impact of these innovative health technologies to be truly realized.