Хирург посмотрел на мою лодыжку и сказал, что это не перелом, а лёгкое растяжение.

Посмотрел is the perfective past tense of посмотреть. It presents the action as a single, completed event: the surgeon took a look at the ankle.

If you used смотрел, that would be imperfective, which often suggests an ongoing process, repeated action, or background description. In this sentence, Russian prefers посмотрел because the doctor examined it once and then gave a conclusion.

So:

• посмотрел = looked / took a look
• смотрел = was looking / looked for some time

The verb посмотреть на means to look at, and after на in this meaning, Russian uses the accusative case.

So:

• лодыжка = nominative
• лодыжку = accusative singular

And мою matches лодыжку in:

• gender: feminine
• number: singular
• case: accusative

That is why you get:

• на мою лодыжку = at my ankle

Because мой has to agree with лодыжку, which is:

• feminine
• singular
• accusative

The feminine singular accusative form of мой is мою.

A quick comparison:

• моя лодыжка = my ankle (subject form, nominative)
• вижу мою лодыжку = I see my ankle (object form, accusative)

So in this sentence, мою is there because the ankle is the object of посмотрел на.

Because что introduces a subordinate clause, equivalent to English that in reported speech.

Main clause:

• Хирург посмотрел на мою лодыжку и сказал

Subordinate clause:

• что это не перелом, а лёгкое растяжение

Russian normally separates this kind of clause with a comma, so:

• сказал, что... = said that...

Here что means that and introduces what the surgeon said.

So:

• сказал, что... = said that...

This is the standard way to report speech indirectly in Russian.
If you wanted direct speech, it would look different, for example:

• Хирург сказал: Это не перелом, а лёгкое растяжение.

But your sentence uses reported speech, so что is the natural choice.

In this kind of diagnosis or identification sentence, это often means it / this.

So:

• это не перелом = it’s not a fracture
• это лёгкое растяжение = it’s a mild sprain

Russian often uses это in statements where English uses it is.

Because in the present tense, Russian normally omits the verb быть (to be).

So English:

• It is not a fracture

Russian:

• Это не перелом

The idea of is is understood automatically.

If you put it in the past or future, then Russian does use a form of быть:

• Это был не перелом, а растяжение. = It was not a fracture but a sprain.
• Это будет растяжение. = It will be a sprain.

Because не ..., а ... is the standard pattern for not X, but Y when the second part corrects or replaces the first.

So:

• не перелом, а лёгкое растяжение = not a fracture, but a mild sprain

By contrast, но usually means but in the sense of contrast, not correction.

Compare:

• Это не перелом, а растяжение. = It’s not a fracture, but a sprain.
  (correction)
• Это перелом, но лёгкий. = It’s a fracture, but a mild one.
  (contrast)

They are both in the nominative singular here.

In sentences like Это перелом or Это растяжение, the noun after это is commonly in the nominative. Russian is basically identifying something: this/it is X.

So:

• перелом = nominative singular
• растяжение = nominative singular

This is why you do not see forms like переломом or растяжением here.

Because лёгкое is an adjective and it must agree with растяжение.

Растяжение is:

• neuter
• singular
• nominative

So the adjective also becomes:

• лёгкое

Compare:

• лёгкий перелом = a mild fracture (masculine)
• лёгкая травма = a mild injury (feminine)
• лёгкое растяжение = a mild sprain (neuter)

In this context, растяжение means a sprain or sometimes more generally a strain, depending on context. With an ankle, English usually says sprain.

Russian medical usage often prefers nouns like:

• перелом = fracture
• вывих = dislocation
• растяжение = sprain/strain

So in this sentence, лёгкое растяжение is naturally understood as a mild sprain.

Because it agrees with хирург, which is grammatically masculine here.

In the past tense, Russian verbs show gender:

• сказал = masculine
• сказала = feminine
• сказало = neuter
• сказали = plural

Since the sentence says Хирург ... сказал, the surgeon is being treated as masculine.

If the speaker wanted to make it clearly female, you would often see:

• Хирург посмотрела на мою лодыжку и сказала...

Хирург specifically means surgeon, not just any doctor.

More general words would be:

• врач = doctor
• доктор = doctor
• хирург = surgeon

So this sentence is specifically saying that a surgeon looked at the ankle.

Yes, лодыжка is a standard word for ankle, especially in everyday speech and medical contexts.

You may also come across щиколотка, which can also mean ankle in many contexts. The two words overlap a lot, though лодыжка is very natural here.

So:

• лодыжка = ankle
• моя лодыжка = my ankle

The sentence has a very natural, neutral word order:

• Хирург посмотрел на мою лодыжку и сказал, что это не перелом, а лёгкое растяжение.

Russian word order is more flexible than English, but this version sounds straightforward and standard. It goes:

1. who did it
2. what they did
3. what they said

You could rearrange parts for emphasis, but this version is the most natural for a plain statement.

Because а is a coordinating conjunction, and in this sentence it links two contrasted parts:

• не перелом
• лёгкое растяжение

Russian punctuation normally puts a comma before а in this kind of contrast:

• не X, а Y

So the punctuation in the second clause is completely standard:

• это не перелом, а лёгкое растяжение