This is a diagnosis that can sound a great deal scarier than it may in fact be. For families considering the adoption of a child with this diagnosis, we provide the following definition of Flexion Deformity.
A flexion deformity of the knee is the inability to fully straighten the knee, also known as flexion contracture. Normal active range of motion (AROM) of the knee is 0° extension and 140° flexion. In people with a flexion deformity, AROM of one or both knees is reduced. It develops as a result of failure of knee flexors to lengthen in tandem with the bone, especially when there is inadequate physical therapy to provide active and passive mobilization of the affected joint.
For more information: https://www.physio-pedia.com/Flexion_Deformity_of_the_Knee