Is the word joelho the same in Brazilian and European Portuguese?

Yes

The word "joelho" is identical in meaning, spelling, and grammatical gender (masculine) in both Brazilian and Continental Portuguese. The only difference lies in pronunciation. In Brazilian Portuguese, the vowels tend to be more open and clearly articulated. In Continental Portuguese, vowels are often more closed or even reduced (nearly silent in some unstressed positions), which can change the "color" of the word, but the word itself remains the same.

Brazilian Portuguese Examples

1. Eu bati o joelho na quina da mesa. (I hit my knee on the corner of the table.)
2. Meu joelho está doendo muito hoje. (My knee is hurting a lot today.)
3. Ele caiu e ralou o joelho no asfalto. (He fell and scraped his knee on the asphalt.)
4. Você precisa cuidar desse joelho. (You need to take care of that knee.)
5. O jogador machucou o joelho durante o jogo. (The player hurt his knee during the game.)

Portuguese (Continental) Examples

1. Bati o joelho na quina da mesa. (I hit my knee on the corner of the table.)
2. O meu joelho está a doer muito hoje. (My knee is hurting a lot today.)
3. Ele caiu e ralou o joelho no asfalto. (He fell and scraped his knee on the asphalt.)
4. Tens de cuidar desse joelho. (You have to take care of that knee.)
5. O jogador lesionou o joelho durante o jogo. (The player injured his knee during the game.)