Officers from the force’s Tactical Roads Policing Team are appealing for anyone who witnessed an incident in Birstall to come forward.
It happened in Loughborough Road at around 5.45pm on Sunday 15th November.
Police were called following a report that a motorcyclist – a 19-year-old man – had fallen from a black Yamaha MT-03.
Officers attended and Leicestershire police said he was taken to hospital to be treated for potentially life-changing injuries.
PC Paul Baker, the investigating officer, said: “As part of our investigation, we are asking for anyone to come forward who saw the motorcyclist prior to him falling – or who saw what happened.
“We are trying to ascertain the circumstances that led to this incident occurring.
“Were you in Loughborough Road or the surrounding area yesterday? Did you see a black Yamaha motorcycle?
“I’m particularly keen to speak to anyone with a dashcam in their vehicle, as well as anyone who saw what happened. Any information you have could help us.”