Hey, I have the same thing.... do you work in an office by any chance? I have been reading about a condition called Lipoatrophia semicircularis (LS) which means a semi-circular line of wasting or atrophy involving fat deposited near the body's surface. This appears as an arching, narrow depression in the skin, typically manifested on the front of thighs (although it can be on the arms, too). This unusual condition was only first reported in the medical literature a few decades ago and seemed to be extremely rare. Rare, that is, other than in certain populations of modern office workers. The ribs in the thighs are typically between 2 to 4 cm high and are typically located at about 72 cm above the ground, which is the standard height of office furniture.
There was also a study:
Clinical observations and pathology
Our story is a remarkable one. In the Spring of 1995, a total of 1100 -bank employees moved to our new office building in Brussels. The building was equipped with new data cabling, new furniture and new telephones, though most of the computer equipment was the same equipment used in our previous premises. In June 1995, a number of women were diagnosed with lipoatrophia semicircularis (LS) for the first time. Six months later, as many as 135 persons had developed this disorder and at the time of writing, nearly 8 years on, we have registrated more than 900 cases. In our local branches and other companies, too, there are increasingly more incidences of this problem. Also in other countries (e.g. France, Italy, U.K. and the Netherlands) LS is diagnosed.(16 - 20)
The disorder is mainly and mostly exclusively afflicting administrative (computer working) people.
Typically, the lipoatrophic zone is localized on the anterolateral side of the thigh, 72 cm above the floor (data gathered on patients wearing shoes) - 72 cm is also the standard height of our office furniture. The lesion can be uni- or bilateral and is between 5 and 20 cm long, about 2 cm wide and 1 to 5 mm deep. The skin remains intact.(fig. 1,2,3) By the onset of the lesions (mostly 2 or 3 months after moving into a new office), some patients mentioned a feeling of heaviness, some experienced a tingling or burning sensation, while others suffered from an increased degree of fatigue.
The lesions could disappear spontaneously after several months, but mostly improved only when people moved to another location in the building, were absent from work for a long time or were on maternity leave. However, the atrophy would come back when they returned to work in the same environment.
LS seems to be reversible. 95% of the retired employees, have no more lesions one year after leaving the company.
In anatomopathological research a perivascular lymphocytic infiltration is observed in the initial phase. In the next phase, there is a decrease in both the volume and number of adipocytes and after that a gradual replacement of the adipocytes by connective tissue. The adipocytes are reabsorbed by lysosomally active macrophages.(18 -19, 21 - 22) It is not clear whether the macrophages are the cause (by producing cytokines) or the consequence of cell destruction.
Echography, MRI or EMG research did not reveal any other abnormalities.
Personal data were recorded and from these it emerged that 84% of the disorders occurred in women, that the pathology was distributed over age groups in accordance with the employees' age pyramid and that there was no link with any other medical disorder among the employees affected.
but I have been on 5:2 for a month and lost 2kg. I noticed about a week or so ago I now have quite a horizontal indentation about 3 inches across in the outside of my right thigh about 2/3rds way up from my knee (poss too much info!) visible and easily felt. My left leg is completely normal. 
