Die Ärztin verbindet die Wunde und sagt, ich solle den Ellbogen heute schonen.

Ärztin is the feminine form of Arzt (doctor).

• der Arzt = a male doctor
• die Ärztin = a female doctor

German often marks professions for gender this way, with -in for the feminine singular.

In everyday German, verbinden often means to connect or to join. But in a medical context, eine Wunde verbinden means to bandage, to dress, or to wrap a wound.

So here:

• die Wunde verbinden = to bandage the wound

This is a very common medical use of the verb.

Wunde is a feminine noun:

• die Wunde = the wound

It is also the direct object of verbindet, so in this sentence the form stays die, because feminine accusative is the same as feminine nominative.

• nominative: die Wunde
• accusative: die Wunde

So the form does not change, even though its role in the sentence is different.

Because Ellbogen is masculine, and here it is in the accusative case.

The verb schonen takes a direct object, so the thing being spared/rested/protected is in the accusative:

• nominative: der Ellbogen
• accusative: den Ellbogen

So:

• ich schone den Ellbogen = I rest/protect my elbow

That is why the sentence says den Ellbogen.

solle is Konjunktiv I, which is often used in reported speech or indirect speech.

The doctor is speaking, and the sentence reports what she says:

• sagt, ich solle den Ellbogen heute schonen

This means something like:

• she says that I should rest my elbow today

Why not ich soll?

• ich soll is the normal indicative form: I am supposed to / I should
• ich solle sounds more like reported speech: she says I should

So solle helps show that this is not the narrator’s own statement, but what the doctor is telling them.

German often allows dass to be omitted, especially in informal or neutral style, when the meaning is still clear.

So both are possible:

• Die Ärztin sagt, ich solle den Ellbogen heute schonen.
• Die Ärztin sagt, dass ich den Ellbogen heute schonen solle.

Both are correct.

The version without dass is a little more compact. In the version with dass, the finite verb solle moves to the end, because dass introduces a subordinate clause.

This clause follows the normal pattern for a clause with a finite verb and an infinitive:

• subject: ich
• finite verb: solle
• object: den Ellbogen
• time expression: heute
• infinitive at the end: schonen

So the structure is:

• ich
  • solle
    • den Ellbogen
      • heute
        • schonen

The infinitive schonen goes to the end because it depends on solle, which works like a modal verb here.

Schonen means to go easy on, to spare, to avoid straining, or to rest/protect something.

In this sentence:

• den Ellbogen schonen = to avoid using the elbow too much / to rest the elbow

It does not mean simply to rest in the sense of lying down. It means being careful not to strain or aggravate that body part.

The comma separates the main clause from the clause that gives the content of what is being said.

Main clause:

• Die Ärztin verbindet die Wunde und sagt

Reported-speech clause:

• ich solle den Ellbogen heute schonen

German uses commas more regularly than English to separate clauses, so this comma is required.

Yes, in everyday spoken German many people would say:

• Die Ärztin sagt, ich soll den Ellbogen heute schonen.

That is very natural and common.

The version with solle is a bit more explicitly reported speech and can sound slightly more formal or written. So:

• ich soll = common in speech
• ich solle = more clearly indirect/reportive

Both are understandable, but solle is the more traditional grammar for indirect speech.

Yes, both exist.

• der Ellbogen
• der Ellenbogen

Both mean elbow. Ellenbogen is often considered the fuller form, while Ellbogen is also standard and widely used. So seeing den Ellbogen here is completely normal.