A foot holding assembly for securing a foot of a patient during a surgical or diagnostic procedure, the assembly comprising: a boot configured to hold the foot of the patient; a rigid sole coupled to the boot; and a pivot arm having a first end coupled to a slider block and a second end coupled to the sole with a rotatable coupling configured to allow the sole to rotate about a tibial axis relative to the pivot arm; wherein the boot is configured to align the patient's tibia parallel with the tibial axis; characterized in that: the first end of the pivot arm is pivotally coupled to the slider block; the pivot arm is configured to rotate about a first axis and a second axis relative to the slider block, wherein the first axis is oriented perpendicular to the second axis; the rotatable coupling includes a shaft rotatably coupled to the second end of the pivot arm; the assembly includes a boot plate mounted to the sole and having an annular portion disposed about the shaft, the annular portion including a plurality of circumferentially spaced detents; and a retainer coupled to the second end of the pivot arm and configured to releasably engage one of the detents to releasably lock the rotational position of the sole about the tibial axis independent of the rotational position of the pivot arm about the first axis and independent of the rotational position of the pivot arm about the second axis. a boot configured to hold the foot of the patient; a rigid sole coupled to the boot; and a pivot arm having a first end coupled to a slider block and a second end coupled to the sole with a rotatable coupling configured to allow the sole to rotate about a tibial axis relative to the pivot arm; wherein the boot is configured to align the patient's tibia parallel with the tibial axis; characterized in that: the first end of the pivot arm is pivotally coupled to the slider block; the pivot arm is configured to rotate about a first axis and a second axis relative to the slider block, wherein the first axis is oriented perpendicular to the second axis; the rotatable coupling includes a shaft rotatably coupled to the second end of the pivot arm; the assembly includes a boot plate mounted to the sole and having an annular portion disposed about the shaft, the annular portion including a plurality of circumferentially spaced detents; and a retainer coupled to the second end of the pivot arm and configured to releasably engage one of the detents to releasably lock the rotational position of the sole about the tibial axis independent of the rotational position of the pivot arm about the first axis and independent of the rotational position of the pivot arm about the second axis. the first end of the pivot arm is pivotally coupled to the slider block; the pivot arm is configured to rotate about a first axis and a second axis relative to the slider block, wherein the first axis is oriented perpendicular to the second axis; the rotatable coupling includes a shaft rotatably coupled to the second end of the pivot arm; the assembly includes a boot plate mounted to the sole and having an annular portion disposed about the shaft, the annular portion including a plurality of circumferentially spaced detents; and a retainer coupled to the second end of the pivot arm and configured to releasably engage one of the detents to releasably lock the rotational position of the sole about the tibial axis independent of the rotational position of the pivot arm about the first axis and independent of the rotational position of the pivot arm about the second axis.