Die Ärztin verbindet die Wunde am Knie.

Because the sentence has two different feminine singular nouns:

• die Ärztin = the doctor
• die Wunde = the wound

In German, die can be both:

• nominative feminine singular for the subject
• accusative feminine singular for the direct object

So here:

• Die Ärztin is the subject: she is doing the action.
• die Wunde is the object: it receives the action.

German case is shown by the article, but for feminine singular, nominative and accusative both happen to be die.

Ärztin is the female form of Arzt.

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

A very common pattern in German is adding -in to a profession or role to make it feminine:

• der Lehrer → die Lehrerin
• der Arzt → die Ärztin

So this sentence specifically says the doctor is a woman.

Here verbindet means bandages, dresses, or treats by putting a bandage on the wound.

The verb verbinden can have several meanings depending on context, such as:

• to connect
• to join
• to bandage / dress a wound

In a medical sentence with die Wunde, the meaning is clearly the medical one: the doctor is bandaging the wound.

Because German main clauses normally follow the V2 rule: the finite verb comes in the second position.

So the structure is:

• Die Ärztin = first element
• verbindet = finite verb in second position
• die Wunde am Knie = the rest

This is standard German word order for a normal statement.

Die Wunde is in the accusative case because it is the direct object of verbindet.

Ask yourself: what is the doctor bandaging?

• The doctor bandages the wound.

That makes die Wunde the thing directly affected by the action, so it is accusative.

Because Wunde is feminine, the article stays die in the accusative singular.

Am is the contraction of an dem:

• an dem → am

So:

• am Knie = an dem Knie

This is extremely common in German and sounds much more natural than saying the full form every time.

Because an is a two-way preposition. That means it can take either:

• accusative for direction or movement toward something
• dative for location

Here the sentence describes the wound’s location, not motion:

• the wound is at/on the knee

So German uses the dative:

• an dem Knie
• contracted: am Knie

Also, Knie is a neuter noun:

• das Knie
• dative singular: dem Knie

German prepositions do not always match English one-for-one.

With body parts and location, an is often used in ways that English might translate as:

• on
• at
• sometimes even by

So die Wunde am Knie means the wound on the knee or at the knee.

You should learn this as a natural German phrase rather than trying to map every preposition exactly to English.

The dictionary form is verbinden.

Verbindet is the 3rd person singular present tense form, used with die Ärztin = she:

• ich verbinde
• du verbindest
• er/sie/es verbindet

So Die Ärztin verbindet ... means The doctor bandages ...

German often leaves out possessive words like her, his, or their when the meaning is already clear, especially with body parts.

So instead of saying something like her wound on her knee, German can simply say:

• die Wunde am Knie

In context, it is usually obvious whose knee is meant.

If needed, German could be more specific, for example:

• die Wunde an ihrem Knie = the wound on her knee

But the shorter version is very natural.

Not really, because the object is die Wunde.

If you say:

• eine Wunde verbinden

that strongly suggests the medical meaning to bandage/dress a wound.

Context is very important in German, and here the medical context makes the meaning clear.

Knie is neuter:

• das Knie

Yes, that matters because the article changes with case:

• nominative: das Knie
• dative: dem Knie

Since an here takes the dative, we get:

• an dem Knie
• am Knie

So the noun’s gender is part of why the phrase looks the way it does.