Hidden pain in the area where the instep bends is referred to as hidden pain in the arch of the foot, which may be caused by overwork, flat feet, fasciitis, and so on. 1. Overexertion: It may be due to long-term walking, running and other sports, which makes the arch of the foot overworked, causing myofascial strain or lactic acid buildup, and thus the hidden pain in the arch of the foot. 2. Flat feet: a kind of foot deformity in which the foot arch is low and flat or disappears. Due to the lesion of the foot arch, the patient may have the foot outwardly turned, the foot arch collapses when standing or walking, and symptoms such as fatigue and hidden pain appear. 3. Fasciitis: mainly due to chronic injury, environmental factors and other causes of pathological changes in the fascia. When fasciitis occurs in the arch of the foot, due to the stimulation of inflammation, the patient may have hidden pain in the arch of the foot. It is recommended that patients with hidden pain in the arch of the foot go to the hospital in time and follow the doctor’s instructions for treatment to avoid delaying the condition.