*breaks* can be both a transitive and an intransitive verb.


Transitive

**A stone *broke* the window.**

"Window" is the direct object. 


Intransitive

**A pane of glass *breaks* when struck sharply with a hard object.**


If you say "My hand breaks" without a direct object, your hand becomes analogous to the "pane of glass" in the second sentence, the example of the intransitive use. That is probably not what you mean to say.  You probably mean to say that at this moment, your hand is injured. Your hand is broken.

**Broken** is the past participle of the verb **break** used adjectivally.

To express that something is currently in a particular state, we use "is" plus the past participle:

The glass is shattered.

The chair is painted.

The table is varnished.

The potato is peeled.


The past participle of many verbs is formed by adding -ed to the verb's bare infinitive:

heat, heated

cook, cooked

paint, painted

But some verbs are irregular and their past participles are formed in another way. For example

sing, sung

break, broken

bring, brought

think, thought