is it caused by any particular gas?
Yes a gas mixture of several such as nitrogen and helium to name a few.
Decompression sickness
The main inert gas in air is nitrogen, but nitrogen is not the only gas that can cause DCS. Breathing gas mixtures such as trimix and heliox include helium, which can also cause decompression sickness.
cause of joint pain in deep sea divers It is termed as "Decompression sickness”. It arises from underwater diving ascent. what are its different types? It was broadly classified in two categories. "Type I" for symptoms involving only the skin, musculoskeletal system, or lymphatic system, and "Type II" for symptoms where other organs, such as the central nervous system are effected. what results in it? It is caused by a reduction in ambient pressure that results in the formation of bubbles of inert gases within tissues of the body.
wiki:5429962
Decompression sickness [SEP] Inert gases
The main inert gas in air is nitrogen, but nitrogen is not the only gas that can cause DCS. Breathing gas mixtures such as trimix and heliox include helium, which can also cause decompression sickness. Helium both enters and leaves the body faster than nitrogen, so different decompression schedules are required, but, since helium does not cause narcosis, it is preferred over nitrogen in gas mixtures for deep diving. There is some debate as to the decompression requirements for helium during short-duration dives. Most divers do longer decompressions; however, some groups like the WKPP have been pioneering the use of shorter decompression times by including deep stops.