premise: Right leg in a brace, a young boy lies on the couch while using his cellphone. hypothesis: The right leg is in a brace.
entailment: Only one leg is described, so 'the' is appropriate; since it is described as in a brace, it is in a brace.|entailment: Right leg in a brace is a paraphrase of right leg is in a brace.|entailment: If his right leg is in a brace, then his leg is in a brace.