Methods, systems and data processing apparatus and methods are described for use in planning and carrying out a surgical procedure on a joint of a subject. The joint includes a first component and a second component, the first and second components being relatively movable. Joint data describing the configuration of the joint is captured while the joint is in a functional state wherein the joint is undergoing its usual load bearing functional behaviour. The joint data is analyzed to determine joint component orientation data specifying the relative orientation of the first and second components. The orientation of prosthetic implants to be used in the surgical procedure to recreate the joint is planned using the joint component orientation data. The planned orientation of the prosthetic implants improves the recreation of the functional state of the joint.