El hueso está roto.

Because Spanish usually uses estar for a state or condition, and broken is being treated as a condition here.

• El hueso está roto = The bone is broken
• estar + adjective often describes how something is at the moment

Using es roto would sound wrong in normal Spanish. With roto, you almost always use estar when you mean something is in a broken state.

Because roto has to agree with hueso in gender and number.

• hueso is masculine singular
• so the adjective must also be masculine singular: roto

Compare:

• El hueso está roto = The bone is broken
• La pierna está rota = The leg is broken
• Los huesos están rotos = The bones are broken
• Las piernas están rotas = The legs are broken

El means the. Spanish usually uses an article with nouns where English also would, and sometimes even where English would not.

Here, el hueso simply means the bone.

Also, if the bone is already known from context, Spanish naturally keeps the definite article:

• El hueso está roto = The bone is broken

Yes, hueso is masculine: el hueso.

There is no perfect rule that works for every noun, but many nouns ending in -o are masculine. So hueso follows a very common pattern.

Useful forms:

• el hueso = the bone
• los huesos = the bones

In Spain, hueso is pronounced approximately like WEH-so.

A few key points:

• The h is silent
• ue forms a diphthong, sounding roughly like we
• So hueso is not pronounced like hoo-eh-so
• It is closer to WEH-so

A rough pronunciation guide:

• hueso → WEH-so
• IPA: [ˈwe.so]

The accent mark shows where the stress goes: es-TÁ.

It also helps distinguish está from esta:

• está = is
• esta = this (feminine), as in esta casa = this house

So the accent is important both for pronunciation and for meaning.

It is both historically a past participle and, in this sentence, it works like an adjective.

It comes from the verb romper = to break.

• romper → roto = broken

In El hueso está roto, roto describes the condition of the bone, so it behaves like an adjective.

This is very common in Spanish:

• La puerta está abierta = The door is open
• El vaso está roto = The glass is broken

Yes, but it means something slightly different.

• El hueso está roto = The bone is broken
  This focuses on the current state.

• El hueso se ha roto = The bone has broken / The bone has become broken
  This focuses more on the event happening.

So:

• está roto = result/state
• se ha roto = action/event leading to that result

Both are correct, but they are not used in exactly the same way.

Normally, no. In Spanish, descriptive adjectives like roto usually come after the noun.

So the normal form is:

• el hueso roto = the broken bone

Putting roto before the noun would sound very unnatural here. For most everyday Spanish, use noun + adjective in this kind of phrase.

You make all the relevant words plural:

• El hueso está roto = The bone is broken
• Los huesos están rotos = The bones are broken

Changes:

• el → los
• hueso → huesos
• está → están
• roto → rotos

The structure is:

subject + estar + adjective

So:

• El hueso = subject
• está = form of estar
• roto = adjective describing the subject

This pattern is very common in Spanish:

• La puerta está cerrada = The door is closed
• La mesa está limpia = The table is clean
• El hueso está roto = The bone is broken

Spanish often uses the definite article with body parts instead of a possessive like my, especially when the owner is already clear from the context.

For example, Spanish often prefers something like:

• Se me ha roto el hueso = I’ve broken a bone / literally, The bone has broken on me

Or:

• Me duele el brazo = My arm hurts / literally, The arm hurts me

So using el with body parts is very normal in Spanish.

Yes, it is grammatically correct and natural, but by itself it sounds a bit context-dependent, because the bone usually refers to a specific bone already being discussed.

For example, it fits naturally in situations like:

• a doctor looking at an X-ray
• someone talking about an injury
• a vet examining an animal

If you wanted a more general statement, Spanish might use a different structure depending on the context. But as a normal sentence meaning The bone is broken, it is perfectly fine.