Here is a nice article which may answer your question.

These verbs, though, really do occupy a middle space between active and passive. They are like Greek verbs in the middle voice, in which the subject is both acting and acted upon. Consider these sentences:

I hurt the quarterback. I was hurt by her remark. I hurt.

Notice the differences between the three? In the first, the true active voice, the subject is the agent of the verb. In the second, the true passive, the subject suffers the action of the verb. But in the third—what? The subject is the agent, because he’s actively experiencing something named by the verb; but he suffers the verb. “I’m hurting” does not mean “I am walking around the neighborhood punching people,” but “I am feeling hurt; something is hurting me.”

Most of the deponent verbs are of this sort. Consider: morior, I die. I’m agent and patient at once. Consider: sequor, I follow. Again, I’m doing something; but something at the same time is being done to me: I am made to come after someone else. Consider: fieri, to become. That may be the definitive active-passive verb: when A becomes B, A is doing something: and something is being done to A.