What is the action of plantar interossei muscles?

This can't adduct the 2nd toe because the plantar interossei don't attach to the 2nd toe. The plantar interossei originates on the medial base of toes 3-5 and attaches to the respective med proximal phalances in the inner sling of said toes.

This can't adduct the 2nd toe because the plantar interossei don't attach to the 2nd toe. The plantar interossei originates on the medial base of toes 3-5 and attaches to the respective med proximal phalances in the inner sling of said toes.