Interesting thought. Was the any investigations suggesting that this was NOT the case prior to the traction? I would suggest traction mainly assists muscles to relax/release and has verry little affect on the movement of disc material. I could propose that, like lying down, the reduced pressure on the discs could lead to some further increase in fluid volume albeit is small.

My first thought is that this type of patient already had the cauda equina issue (it this was actually a patient and not a hypothesis). Furthermore that traction aggravated the symptoms and that this lead to further investigation which demonstrated the cauda equine issue.

On a traction note: it can be a useful treatment and patients that have benefited from it in the past tend to come in asking for it. It is however poorly applied and is an acquired skill. I remember in Australia there were an excellent set of traction videos you could get you hands on that really looked into how, why, when, how long etc to use traction. These were excellent teaching aids, much more than the undergraduate degree.