A comprehensive laboratory investigation was conducted in which four large-scale structural concrete bridge knee joint units were tested. These units represented an as-built joint, and a repair, a retrofit, and a redesign of the as-built joint, and incorporated differing detailing including haunching, prestressing, and variations in the quantity of specially-placed joint reinforcement. Extensive experimental data led to an improved understanding of the force transfer mechanisms developed within joints of this type. A discussion of test unit response and a review of the most relevant data measured from each test are presented.