Ude-Hishigi-Hiza-Gatame(腕挫膝固?) is one of the official 29 grappling techniques of Kodokan Judo. It is one of the nine joint techniques of the Kansetsu-waza list, one of the three grappling lists in Judo's Katame-waza enumerating 29 grappling techniques.  All of Judo's competition legal joint techniques are arm locks.
Hiza refers to knee. Gatame refers to pin. This technique is using the knee to joint lock and pin the opponent. Once the opponent is face down an arm bar can be applied using the knee on the opponents elbow, the opponents hand must be pinky up. Upwards pressure can be applied on the wrist while downward pressure is applied with the knee on the elbow. The inside of the knee area can also be used to torque the elbow/shoulder from a bottom transition.