Foot and ankle problems usually fall into the following categories:
- Acquired from improper footwear, physical stress, or small mechanical changes within the foot.
- Arthritic foot problems, which typically involve one or more joint.
- Congenital foot problems, which occur at birth, are generally inherited.
- Infectious foot problems, which are caused by bacterial, viral, or fungal disorders.
- Neoplastic disorders, usually called tumors, which are the result of abnormal growth of tissue and may be benign or malignant.
- Traumatic foot problems, which are associated with foot and ankle injuries.
The most common cause of yellow discoloration in the toenails is a fungal infection. The fungus often develops underneath the nail, resulting in it becoming thick, raised, and yellow in color. Other potential causes for yellow discoloration of the nail include diabetes mellitus and lymphedema (chronic leg swelling). Yellow staining of the nails can also occur in individuals who use nail polish. A stained nail may take several months to grow out.