There are many causes of pain in the left big toe joint, the most common of which are bacterial infection, arthritis, bunion deformity, external factors, etc. The details are as follows: First, bacterial infection: the presence of bacterial infection in the left big toe joint will lead to localized pain, swelling, and elevated skin temperature, and the localized redness will occur. Arthritis: Gouty arthritis, osteoarthritis, rheumatoid arthritis, rheumatoid arthritis, can also lead to significant pain in the left big toe joint. Bunion deformity: If the patient has bunion deformity, it will also lead to obvious pain symptoms in the left big toe joint. External factors: Localized external forces, causing joint capsule damage, dislocation, and fracture, can also lead to significant pain in the left big toe joint.