Left foot radical — indexing radical for
跑. Pictographically
口 (knee/calf) over
止 (footprint), the full leg-and-foot graph. As left-side radical
足 takes a slightly squared form. Anchors
跑 in the foot-motion family alongside
跳 (jump),
踢 (kick),
路 (road),
跟 (follow). All members are things done with feet.