I was wondering if you can help site some examples for spinal conditions (e.g. spondylolisthesis etc.) with regards to flexion and extension biases.

With some back conditions, specific positions are known to help manage symptoms. These positions are known as biases. There are three types of biases: flexion, extension and non-weight bearing. Taken together, these biases are called direction preferences.

If the patient’s back feels better and/or symptoms abate when they bend forward, it’s likely that the injury or condition being experienced has a flexion bias. For example, spinal stenosis, which is a condition that narrows the space in the intervertebral foramen, generally has a flexion bias. Many patients with spinal stenosis find that bending their spine forward (aka spinal flexion) make it feel better. The reason is that bending forward creates more space in the intervertebral foramen. This, in turn, allows the nerve that passes through the foramen to do so without being touched or pressured by nearby bone. Other conditions that usually have a flexion bias include spondylosis and spondylolisthesis. For injuries and condition with a flexion bias, symptoms tend to increase when the back is extended (arched).

The opposite of a flexion bias is an extension bias. An extension bias occurs when the movement of arching the back makes the symptoms feel better. Examples of conditions that tend to have extension biases are herniated and bulging discs. Patients with either of these conditions often find that when they bend forward (into spinal flexion) their symptoms worsen, and as already stated, when they arch their back, it feels better.

Flexion bias (along with extension bias and non-weight bearing) are part of a non-patho-anatomical system of classification for mechanical low back pain, specifically disc problems, facet joint pain or dysfunction, sacroiliac joint dysfunction and spinal instability due to a problem in the pars (which is an area at the back of a vertebra where processes emanate. These processes become part of the facet joints).

Anne Asher, CPT. What Is the Definition of Flexion Bias? 2017.

Here is a link to a related question on the different types of spinal vertebral conditions