A hernia or protrusion affecting a joint, or a swelling of the joint capsule.
From Greek 'arthron' (joint) + 'kele' (hernia, swelling, or protrusion). The '-cele' suffix became medical terminology's standard way to describe hernias and protrusions in various body areas.
The '-cele' suffix is like a medical badge—whenever you see it, you know something is bulging or herniating: hydrocele (fluid around testicles), meningocele (brain membrane protruding), varicocele (enlarged veins).
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