A more thorough explanation:

Definition: Joinder of issue is a legal term that refers to the point in a lawsuit when both parties have accepted that a particular issue is in dispute. This happens when the defendant challenges some or all of the plaintiff's allegations of fact or when it is known which legal questions are in dispute. It usually occurs when pretrial discovery is complete.

Example: In a personal injury case, the plaintiff may allege that the defendant was negligent and caused the accident that resulted in the plaintiff's injuries. The defendant may deny these allegations and argue that the plaintiff was actually at fault for the accident. Once both parties have presented their arguments and evidence, and it is clear that the issue of fault is in dispute, the issue is joined.

Explanation: In this example, the issue of fault is in dispute between the plaintiff and defendant. The plaintiff alleges that the defendant was at fault, while the defendant denies this and argues that the plaintiff was at fault. Once both parties have presented their arguments and evidence, and it is clear that the issue of fault is in dispute, the issue is joined. This means that the parties have accepted that this particular issue is in dispute and will need to be resolved through further legal proceedings.