Cuando termine el reposo y la rodilla deje de estar hinchada, limpiaré el cuarto y colgaré una foto sobre el estante.

Because after cuando referring to a future event, Spanish normally uses the present subjunctive, not the indicative.

So:

• Cuando termine el reposo... = When the rest period is over...
• ...y la rodilla deje de estar hinchada... = ...and the knee stops being swollen...

This is very common in Spanish:

• Cuando llegue, te llamo. = When he/she arrives, I’ll call you.
• Cuando tenga tiempo, lo haré. = When I have time, I’ll do it.

English uses a present form after when, and Spanish uses the present subjunctive in this kind of future situation.

In this kind of sentence, Spanish normally does not say cuando terminará or cuando dejará to mean when it ends / when it stops in the future.

Instead, Spanish uses:

• cuando + present subjunctive for a future condition or event
• a future or present form in the main clause

So the pattern is:

• Cuando termine..., limpiaré...

Not:

• Cuando terminará..., limpiaré...

This is one of the biggest differences from what English speakers expect.

It literally means stops being swollen.

The structure is:

• dejar de + infinitive = to stop + -ing / to stop doing something

Examples:

• dejar de fumar = to stop smoking
• dejar de llover = to stop raining
• dejar de estar hinchada = to stop being swollen

So here, the sentence is describing the moment when the knee is no longer in that swollen state.

Because estar is used for a temporary state or condition, and being swollen is a temporary physical condition.

So:

• estar hinchada = to be swollen
• ser would sound wrong here because it suggests a more permanent or defining characteristic

This is a classic ser vs estar case:

• La puerta está abierta = the door is open right now
• La puerta es grande = the door is big by nature

Swelling is clearly a temporary condition, so estar is the correct choice.

Because hinchada agrees with la rodilla, which is feminine singular.

Agreement in Spanish works like this:

• el brazo está hinchado
• la rodilla está hinchada
• las rodillas están hinchadas

The adjective has to match the noun in gender and number.

Spanish often uses the definite article with body parts when the owner is obvious from the context.

So instead of saying my knee, Spanish often says the knee:

• Me duele la cabeza = My head hurts
• Tengo levantada la mano = I have my hand raised
• la rodilla deje de estar hinchada = the knee stops being swollen

To an English speaker, this can feel strange, but it is completely normal in Spanish.

Most naturally, el reposo is the subject, so it means:

• when the rest period is over
• literally, when the rest ends

Spanish often allows this kind of structure where a thing or period ends:

• Cuando termine la clase... = When class ends...
• Cuando termine la película... = When the film ends...

In some contexts, cuando termine el reposo could also be understood as when I finish the rest period, but here the most natural reading is that the rest period itself comes to an end.

Because they describe what the speaker will do after those future conditions are met.

The structure is:

• condition in the subordinate clause: Cuando termine... y deje...
• future result in the main clause: limpiaré... y colgaré...

So the speaker is saying that these actions will happen later, not now.

Spanish could sometimes use the present for near-future meaning in conversation, but the future tense here is very clear and standard.

Because both verbs are separate main actions, and each one needs its own finite verb form.

So Spanish says:

• limpiaré el cuarto y colgaré una foto

not:

• limpiaré el cuarto y colgar una foto

The second version is ungrammatical because colgar would be an infinitive with no verb controlling it.

English also normally repeats the finite verb idea here:

• I will clean the room and hang a photo English allows the second verb in bare form after will, but in Spanish there is no single auxiliary here that covers both verbs separately in that way. Each coordinated verb is fully conjugated.

Here reposo means rest, especially in a medical or recovery sense.

Depending on context, it can suggest:

• resting after an injury
• taking it easy
• prescribed rest by a doctor

So in this sentence it sounds like the person is recovering and waiting for the knee to improve before doing those tasks.

Yes, it is understandable and natural, though the exact nuance can vary.

In Spain:

• cuarto can mean room
• habitación is also very common, especially for a bedroom or a more neutral room

So limpiaré el cuarto is perfectly understandable. Depending on region and context, some speakers might more naturally say la habitación.

This is a very good question because sobre can be a little tricky.

Most often, sobre means:

• on
• over
• above

In this sentence, with colgaré una foto, many learners would understand it as I’ll hang a photo above the shelf or over the shelf, probably on the wall.

If you wanted to say the photo is physically placed on the shelf, Spanish would more naturally say:

• en el estante
• or sometimes encima del estante, depending on the exact meaning

So with colgar una foto sobre el estante, the most natural image is a picture hanging in the space above the shelf.

Because the sentence begins with a subordinate clause:

• Cuando termine el reposo y la rodilla deje de estar hinchada, ...

After that introductory clause, Spanish normally uses a comma before the main clause:

• ..., limpiaré el cuarto y colgaré una foto...

This is similar to English punctuation:

• When the rest period is over and the knee is no longer swollen, I’ll clean the room...

Because Spanish often leaves subject pronouns out when the verb ending already makes the subject clear.

• limpiaré already means I will clean
• colgaré already means I will hang

So yo is not necessary unless the speaker wants emphasis or contrast:

• Yo limpiaré el cuarto, no tú. = I will clean the room, not you.

In normal Spanish, omitting the pronoun is more natural.

Sometimes, yes, especially in informal speech, Spanish can use the present to talk about the near future:

• Cuando termine el reposo y la rodilla deje de estar hinchada, limpio el cuarto y cuelgo una foto.

But in this sentence, limpiaré and colgaré sound clearer and more standard for a planned future action.

So:

• future tense = very clear, explicit future
• present tense = possible in some contexts, usually more conversational or immediate

The version you have is perfectly natural and safe.