system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why do joints sometimes "catch"?

For example when you try to straighten your elbow or ankle and it feels like something kinks in the joint so much that you couldn't possibly force the movement any further without causing serious discomfort... And then a minute later you have full range of motion with zero pain again.
gpt
Sometimes it's literally just that. 

Bones are pulled by muscles that attach via tendons. Sometimes those tendons get caught in the joint and don't allow you to complete the movement until you reverse and allow the tendon to get unstuck.