אם הברכיים כואבות, אל תרוצי היום; תלכי לאט ותחזרי הביתה מוקדם.

Because the sentence is addressing one female person.

All three are second-person singular feminine forms:

• תרוצי = you will run / run
• תלכי = you will walk / walk
• תחזרי = you will return / return

In Hebrew, verbs often show person, number, and gender, so the speaker does not need to say את for you.

If the sentence were addressed to a man, you would get:

• אל תרוץ
• תלך לאט
• ותחזור הביתה מוקדם

ברכיים is the form for knees, and the ending -יים is the old dual ending, which is especially common with body parts that usually come in pairs.

Examples:

• עין → עיניים = eye → eyes
• אוזן → אוזניים = ear → ears
• ברך → ברכיים = knee → knees

In modern Hebrew, forms like ברכיים usually behave grammatically like a plural noun.

Because ברכיים is treated as a feminine plural noun.

The singular noun is:

• ברך = knee, and it is feminine

So when the knees are the subject, the verb/predicate must agree:

• הברך כואבת = the knee hurts
• הברכיים כואבות = the knees hurt

Here כואבות is the feminine plural form of כואב / hurting, aching.

In sentences like this, it behaves like the present-tense form of the verb לכאוב = to hurt / to ache.

Hebrew present-tense forms often look like adjectives and agree in gender and number, so to an English speaker they can feel like a mix of both.

So:

• הברכיים כואבות literally looks something like the knees are aching
• Natural English: the knees hurt or your knees hurt

אם means if.

So:

• אם הברכיים כואבות = if the knees hurt

This introduces a condition, just like English if.

Hebrew does not need a word for your here if the context already makes it clear whose knees are meant.

Because אל is used for a negative command: don’t ...

So:

• אל תרוצי = don’t run

By contrast, לא usually negates ordinary statements:

• היא לא רצה = she is not running
• את לא תרוצי מחר = you will not run tomorrow

A very common rule for learners is:

• אל + future form = don’t ...

That is normal in Hebrew.

After אל, Hebrew usually uses a future-tense form to express a prohibition:

• אל תרוצי = don’t run
• אל תלכי = don’t go

So even though the form is technically future, the meaning is command/instruction.

This is one of the places where Hebrew form and English translation do not match one-to-one.

Hebrew often uses future forms as commands, especially in everyday speech and neutral instructions.

So both of these are possible:

• לכי לאט = walk slowly
• תלכי לאט = walk slowly

And:

• חזרי הביתה מוקדם
• תחזרי הביתה מוקדם

The future forms often sound a bit more natural, less abrupt, or more conversational in many contexts.

So in this sentence:

• תלכי לאט ותחזרי הביתה מוקדם

is a very normal way to give advice or instruction.

הביתה means homeward / home / to the house, using the old directional ending -ה.

This ending can add the idea of toward a place.

So:

• הביתה = homeward / home
• העירה = to the city
• החוצה = outside

In modern Hebrew, הביתה is a very common fixed word meaning home in the sense of going home.

So:

• תחזרי הביתה = return home / go back home

Because here מוקדם functions like an adverb, meaning early.

When Hebrew uses an adjective adverbially, it is often left in the masculine singular form.

So:

• לחזור מוקדם = to return early
• היא חזרה מוקדם = she returned early

Even though the person is feminine, מוקדם does not change here.

This is similar to English, where early also stays the same no matter who does the action.

Because Hebrew usually drops subject pronouns when the verb already shows who the subject is.

For example:

• תרוצי already means you (singular feminine) will run
• תלכי already means you (singular feminine) will walk

So saying את is usually unnecessary unless you want emphasis or contrast.

That is why Hebrew often sounds more compact than English.

Hebrew often uses the definite form where English might prefer a possessive like your.

So:

• אם הברכיים כואבות literally = if the knees hurt

But in real meaning, depending on context, it can easily mean:

• if your knees hurt
• if the knees are hurting

This is especially common with body parts, where Hebrew may use the + body part instead of saying your every time.

The semicolon separates two closely connected parts:

1. If the knees hurt, don’t run today
2. Walk slowly and return home early

So it marks a stronger break than a comma, but it still keeps the ideas linked.

It is basically showing:

• first: the condition and warning
• then: the advice about what to do instead

The sentence would still be understandable with a different punctuation choice, but the semicolon makes the structure especially clear.