Leg Length Discrepency or feeliing of one, what causes it?

Questions from patient:

"My recovery has been going well but I have just, noticed a difference in leg length, not when standing or walking, but when I sit, or bend my legs while standing.

When I stand with feet together then bend my legs with knees together the distance that my right knee cap extends is about 2 inches longer (more protruded) than my left. As well when I sit in an upright chair, back straight, knees together and feet together I also see my right left knee cap extends about 2 inches longer than my left. I certainly don't have a leg length difference when standing or walking, at least not detectable. If there was that much difference I would notice when walking.

Can you comment if this is normal? Is it due to weak hip muscles following surgery? I can even out the length difference by adjusting my hip, but that requires intent. I'm a little concerned and would appreciate your input on this. 

Answer from Dr. Bose

Dear Peter ,
THanks for the mail.
Many patients have commented to me on this phenomenon.
This is due to tight muscles ( stretched).

As a rule muscles get tight and contracted in any arthritic stiff hip. This contracture of muscles is 3 dimensional and not in one plane.
This will also get corrected as a rule as the muscles slowly relax to their normal , correct length in a matter of few weeks.

This apparent temporary imbalance is most prominent in the proximal segment when the patient is sitting because the pelvis gets fixed while sitting , shutting out the spinal compensation to some extent. The spinal compensation is brought into play when the patient is standing/lying down.

However if you carefully look at leg length the  temporary leg length difference will also be detected while standing , lying down but to a much smaller degree.

I hope this helps.
The team joins me in wishing you and yours the very best
with best regards
vijay bose
chennai