During ascent of sea diving a diver developed severe knee joint pain. What can be the reason for his problem?

Decompression Sickness (DCS): DCS is caused by the formation of bubbles from dissolved ine gas (usually nitrogen) during or after ascent (decompression) from a compressed gas dive. Decompression sickness occurs when the ascent is too rapid and gas bubbles form and cause damage depending on their location (eg, coronary, pulmonary, spinal or cerebral blood vessels, joints, soft tissue). Divers control their ascent for a given depth and time exposure using algorithms that often include periods where ascent is halted for a prescribed period at different depths to allow time for gas wash-out ("decompression stops"). Ref: Bennett M.H., Mitchell S.J. (2012). Chapter e52. Hyperbaric and Diving Medicine. In D.L. Longo, A.S. Fauci, D.L. Kasper, S.L. Hauser, J.L. Jameson, J. Loscalzo (Eds), Harrison's Principles of Internal Medicine, 18e.