A recent article entitled "Risk of blood clot after surgery higher and lasts longer than previously thought" raises an interesting point especially in light of recent discussions about public perceptions regarding medical care.  
The risk of venous thromboembolism (a collective term for deep vein thrombosis and pulmonary embolism) is known to increase after surgery, particularly after major orthopaedic (joint) surgery. The risk is thought to be highest during the first few weeks after an operation but little is known about the exact pattern and scale of this increased risk.
This paragraph raises an important question.  What is the scientific or medical basis for phrases like "is thought to be"?  How was the determination made regarding the length of time that a risk persisted?

It appears that from this article, no one knew the answer and the problem hadn't been researched to any significant degree.  In short, medical advice and practice was occurring that apparently had little basis in actual scientific data.

What is also interesting is how no one in the medical community seems to acknowledge where this viewpoint came from.  
"What is most striking is that not only is the risk higher, but that it lasts much longer than people have thought," said Dr. Jane Green, a clinical epidemiologist at the University of Oxford and a leader of the team reporting the findings in the Dec. 4 online edition of BMJ.

http://www.palmbeachpost.com/health/blood-clot-threat-after-surgery-worse-than-thought-98670.html
Who are these "people" that are being referred to?
The linked prospective cohort study by Sweetland and colleagues (doi:10.1136/bmj.b4583) is a wake-up call to all surgeons.
http://www.bmj.com/cgi/content/extract/339/dec03_1/b4477

"The extent of the problem is bigger than we thought," said Dr. Alexander Cohen, an honorary consultant vascular physician at King's College Hospital in London, who wrote an accompanying editorial.
http://www.palmbeachpost.com/health/blood-clot-threat-after-surgery-worse-than-thought-98670.html

I'm not intending to arbitrarily criticize the medical community or science, but rather to point out a glaring problem that seems too readily glossed over.  The unfortunate reality of this paper demonstrates that despite years of performing these surgeries, and obvious anecdotal evidence indicating potential problems.  No one took the time to put scientific data behind the prevailing treatments.

The question that begs to be asked, is what the basis was for determining adequate treatment in the absence of any bonafide data.  I don't see how this can be described as anything but lackadaisical.

I want to be clear that the problem I'm describing is not that surgeons or scientists didn't know the answer.  The problem is that they all acted as if they did.
These findings indicate that we should be investigating the rates of venous thromboembolism,the use of preventive anti-clotting therapy, and the length of therapy in a wider range of patients.
That would probably be a good idea.

Original article:
http://www.bmj.com/cgi/reprint/339/dec03_1/b4583

See also:
http://www.science20.com/news/25_000_uk_deaths_per_year_due_to_poor_blood_clot_treatment