3 months post op silicone implant, I noticed some rippling. Is this normal? (photo)

I don't think this is an implant ripple since you do not feel it with your arm down. It appears that your pec muscle is pulling a bit on your skin when you elevate your arm. Your breast tissues must be thin for this to be this visible. Hopefully this will be acceptable over time, If not then I am sure your surgeon could discuss some muscle releasing or a little fat grafting or both to improve this. Good luck

Rippling can occur with both silicone and saline implants especially more so in women with very little breast tissue. If it bothers you speak with your plastic surgeon regarding some options. 

Rippling can occur with either saline or gel implants in women with very little breast tissue. Fat transfer, if you have any available fat, or soft tissue grafts like Alloderm can be helpful.  If it is minimal rippling, you might leave it alone.

Rippling can occur when there is not enough soft tissue coverage for the implants. Strattice can be used to camouflage the area.

Greast question.  My father would normally tell me just never raise your arms and there won't be any ripples!  I believe that the line/crease/ridge is from the edge of your pectoralis muscle.  It rarely gets worse, in fact it usually gets better over time.  A revision surgery with muscle release or fat transfer will usually help with this situation.Best of luck.Dr Taranow

Chances are that this is not what most would call a ripple, but rather is an indentation from the lower edge of the pectoralis major muscle. That is why it is only visible in the photographed position. Your surgeon can easily verify this on examination. This may get better, it is doubtful that it may get worse. All the best. 

I don't think I would do anything right now.  You are very lean and do not have much native breast tissue.  It is not uncommon to be able to see or feel even a silicone implant when you raise your arms or bend forward.  I suggest keeping an eye on it and asking you PS for his/her input at your one year check up.