On February 7, 2020, about 0105 eastern standard time, PSA Airlines flight 5634, a Canadair CRJ-900, N610NN, encountered turbulence during enroute descent to McGhee Tyson Airport (KTYS), Knoxville, Tennessee. Of the 73 passengers and crew onboard, one flight attendant received serious injuries and there were 21 minor injuries. The airplane sustained minor damage. The regularly scheduled domestic passenger flight was operating under the provisions of 14 Code of Federal Regulations Part 121 from Charlotte Douglas International Airport (KCLT), Charlotte, North Carolina, to KTYS. The accident flight departed 4 hours late due to the late arrival of the inbound airplane in KCLT because of persistent severe weather that had been in the area. According to the flight crew, they kept the seatbelt sign illuminated for the entire flight because of the late night and weather in the area. They indicated that the takeoff, climb, and cruise were uneventful. Most of the flight was conducted at flight level (FL) 220 in clear air, with clouds beneath. As they approached KTYS, the flight was cleared to descend at pilot’s discretion to 13,000 feet. During the descent, the onboard radar was on but did not depict any precipitation in the cloud layer below them. In the early stages of the descent, the flight began entering and exiting various cloud layers and experienced very light/intermittent chop. At about FL 185, the flight went into a cloud and encountered severe turbulence, causing the autopilot to disengage and the airplane pitched nose down rapidly. The pilot flying reduced power, leveled the wings, and the airplane quickly exited the clouds into visual meteorological (VMC) conditions again. The flight continued to experience moderate turbulence during the descent. The captain called back to check on the flight attendants (FA) and passengers but initially received no reply. A short time later, the captain called back again and was informed by a dead-heading flight attendant (FA) that both FAs had been injured. At the time of the turbulence encounter, the forward FA was preparing the galley for landing and was thrown to the ceiling and back to the floor, injuring both ankles. The FA could not stand, and a dead-heading pilot helped her to a passenger seat. The aft FA was conducting final compliance checks in the cabin and was also thrown to the ceiling and back to the floor, causing her to black out for a short time. Multiple passengers received various injuries, that included head bumps/bruises, scrapes, and anxiety issues. Two dead-heading FAs assumed the duties of the two injured FAs for the remainder of the flight. After landing, paramedics met the airplane at the gate and the two FAs and several passengers were transported to the hospital. The forward FA was diagnosed with fractures in both ankles. Post accident examination of the weather data determined that the turbulence encounter occurred in a strong sheared environment with a 155-knot jet stream. There were several pilot reports (PIREPs) of moderate to severe turbulence in the area, and there was a National Weather Service SIGMET current for severe turbulence in the area.