Background: It has been widely recommended that clinical trials on people with low back disorders should have a greater focus on subgroup specific treatment in order to increase the likelihood of clinically meaningful effects being demonstrated. The McKenzie approach to assessing and treating patients with a directional preference is a potentially useful and widely used clinical method in providing specific treatment. Studies to date have not used a clearly defined and appropriately detailed clinical protocol for the McKenzie approach that is reproducible in the clinical or research setting. Objectives: This paper presents a detailed classification and treatment protocol for people with clinical features thought to be indicative of reducible discogenic pain with a directional preference that is responsive to mechanical loading strategies. Discussion: A pathoanatomical interpretation of the McKenzie approach, classification principles and particular treatment components in the clinical protocol are discussed. Conclusion: The described clinical protocol will be used in the Specific Treatment for Problems of the Spine trials comparing specific physiotherapy to evidence-based advice.