travelling on foot; journeying on foot; hiking
A somewhat old-fashioned or literary term for traveling on foot, often with a lighthearted or rustic feel. The expression comes from the image of one's knees (膝) being the 'chestnut horse' (栗毛) that carries you.
Travelers in the old days walked from Edo to Kyoto on foot.
It's not bad to go along the mountain path on foot.
Literally 'knee chestnut horse', a humorous metaphor likening one's knees to a horse that carries the traveler. The phrase was popularized by the Edo-period comic novel 東海道中膝栗毛 (Tōkaidōchū Hizakurige).