The left foot feels sore and weak, mainly involving the following factors: the first is that the blood circulation in the left calf is affected, commonly due to causes such as cold in the calf and vascular diseases of the calf. This leads to poor blood circulation in the lower leg, blood stagnation, failure to remove metabolites in a timely manner, and irritating weakness and soreness of the foot. The second cause is seen in lumbar disc herniation. Commonly, for example, the herniated discs of lumbar 4 and 5 and lumbar 5-sacral 1 compress the nerve roots, resulting in the corresponding soreness and weakness of the foot. The third cause is seen in systemic metabolic diseases. Generally this disease presents with symmetrical limb symptoms, but a few patients may also present with unilateral limb conditions, such as diabetes, kidney disease, and so on. The fourth cause is foot strain. The strain on the foot due to frequent standing and walking or overload activities, resulting in a sore and weak feeling.