Ganglions are small sacs (cysts) filled with clear, jelly-like fluid that often appear as bumps on the hands and wrists. They can also develop on feet, ankles, knees, or shoulders. They are not cancerous. A ganglion can grow out of a joint capsule, which surrounds and protects the joint, or a tendon sheath, which covers the tendon (the rope-like fibers connecting muscle to bone). Most people with ganglions notice that the bumps appear suddenly. Follow the links below to read WebMD's comprehensive coverage of ganglions.