United Airlines flight 152 encountered moderate turbulence while descending through 10,000 feet to Hong Kong International Airport. As a result, a flight attendant (FA) sustained a serious injury. During the descent, the seatbelt sign was illuminated, and the flight crew had instructed the flight attendants to prepare for landing. The aircraft passed through a thin cloud layer at approximately 10,000 feet, followed by another cloud directly ahead. No radar returns were observed on the aircraft’s weather radar display and onboard weather applications showed no indications of an adverse ride. While passing through the top of the second cloud, the aircraft experienced about two seconds of moderate turbulence. The flight continued without further incident and landed uneventfully. After taxiing to the gate, the crew was informed that the number 4 FA was injured. At the time of the turbulence encounter, the number 4 FA was in the aft galley and was thrown to the floor, impacting her head, wrist, and buttocks. MedAire was consulted, and the FA was advised to seek medical evaluation upon arrival at the hotel. She was later transported to a local hospital, where she was diagnosed with a serious injury. At the time of the turbulence encounter, there were no active forecasts indicating turbulence in the area.