Hitchhiker thumb The condition known as "hitchhiker's thumb" means, that the distal phalanx of the thumb, when the thumb is extended (as in a "thumbs-up"), can extend backwards toward the nail and outwards at an angle of up to, or more than, 90 degrees from the thumb, whereas normally it will extend straight out with little backward bending. Abducted thumb HP:0040021 HP:0001234 UMLS:C1857269 Hitchhiker thumb HP:0009620 With the hand relaxed and the thumb in the plane of the palm, the axis of the thumb forms an angle of at least 90 degrees with the long axis of the hand. Radial deviation of finger Deviation of the thumb Abnormality of the distal phalanx of the thumb