У мене болить щиколотка.

In this pattern, у мене literally means something like at me / with me, but idiomatically it is the normal way to express a state or symptom affecting you.

So Ukrainian often says:

• У мене болить голова = My head hurts / I have a headache
• У мене болить щиколотка = My ankle hurts

This is more natural in Ukrainian than building the sentence around my.

Because after у in this possessive-style construction, Ukrainian uses the genitive case.

So:

• я = I
• мене = me / of me (genitive/accusative form, depending on the construction)

In у мене, the form is genitive: at me / with me.

This whole chunk functions like I have or as for me in English.

Because щиколотка is the grammatical subject of the verb болить.

Literally, the structure is close to:

• At me hurts the ankle

So the thing that hurts — щиколотка — stays in the nominative singular, and the verb agrees with it.

Because щиколотка is singular.

Compare:

• У мене болить щиколотка = My ankle hurts
• У мене болять щиколотки = My ankles hurt

So болить is singular, and болять is plural.

Yes, it is understandable and grammatically possible, but it is less neutral.

For everyday symptoms, Ukrainian more naturally prefers:

• У мене болить щиколотка

Using моя can sound more emphatic or contrastive, as if you are stressing my ankle specifically, not someone else’s.

So for a normal medical complaint, У мене болить щиколотка is the better default.

Yes. У and в often alternate in Ukrainian for smoother pronunciation. The meaning is the same.

So both of these work:

• У мене болить щиколотка
• В мене болить щиколотка

You will often hear both. The choice is usually about sound and flow, not grammar meaning.

Yes, if the context already makes it clear that you are talking about yourself.

For example, if a doctor asks what hurts, you can say:

• Болить щиколотка.

That means My ankle hurts in context.

But if you want to make the speaker explicit, especially out of context, у мене is helpful and natural.

No. Ukrainian word order is flexible, but the neutral, standard order here is:

• У мене болить щиколотка.

Other orders are possible for emphasis:

• Щиколотка у мене болить. — emphasizes ankle
• Болить у мене щиколотка. — more conversational or marked

A learner should usually start with У мене болить щиколотка.

Болить is a verb and is used when you name what hurts:

• У мене болить щиколотка.
• У мене болить спина.

Боляче means painful / it hurts more generally:

• Мені боляче. = I’m in pain / It hurts.
• Мені боляче ходити. = It hurts to walk.

So if you want to say which body part hurts, болить is the usual choice.