system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What actually happens when we crack our knuckles/joints?

Also, can it cause joint complications in later life? There isn't much evidence on the internet.
gpt
The physical mechanism causing a cracking sound produced by bending, twisting, or compressing joints is UNCERTAIN. Suggested causes include: 
Cavitation within the joint—small cavities of partial vacuum form in the synovial fluid and then rapidly collapse, producing a sharp sound.
Rapid stretching of ligaments.
Intra-articular (within-joint) adhesions being broken.