Despite the advantages of tangible interaction, physical controls like knobs seem to be disappearing from a wide range of products in our everyday life. The work presented in this paper explores how physical controls can become dynamic, in terms of both shape, and haptic force feedback. The paper contains two strands of work: First, we present a study that explores the relationship between haptic force feedback and different knob shapes, evaluating twelve distinct haptic stimuli in relation to six widely used knob shapes. Second, based on the insights collected in the study, we present the design of DynaKnob, a shape changing knob that can change between four different knob shapes. DynaKnob illustrates how dynamic content control, can be combined with dynamic shape and force feedback. Both the study and the design of DynaKnob contribute to understanding how adaptive physical interface controls could be designed in the future.