How can I tell if I have inner varicose veins in my legs?

Ultrasound. Significant failures of veins inside legs usually have some kind of evidence on the surface, such as visible varicose veins, skin changes, swelling, etc. And symptoms such as aching, throbbing when standing or sitting for a long period. An experienced phlebologist can usually determine this by history and exam. If necessary, an ultrasound can be performed to examine the inside veins.
Probably can't tell. You probably aren't going to be able to tell by looking. Even with a trained eye, specialists often can't tell. As the others have mentioned, the only way to know for sure is with ultrasound.
Ultrasound. Venous insufficiency ultrasound will look for superficial and deep venous reflux.
You could. You could have varicose veins beneath the skin that are not visible on the surface. If you have pain you should a vascular surgeon.
Thigh Varicose Veins. Varicose veins of the thigh are very common and usually would appear as bulging, grape-like veins in the upper inner thigh. If you have any concerns about having varicose veins then you should see a vein specialist for a full venous evaluation including a venous ultrasound.

Related Questions

Can an X-ray taken of the leg show that there was a venous closure procedure (varicose veins) done 5 years ago? Is it important to tell a doctor this?

Sonogram not X-RAY. A venous ultrasound to look at the saphenous veins would show if the saphenous vein has been closed. 5 years since the closure the vein would be threadlike or non existent. If the vein appeared normal, then it either wasn't treated by closure or the closure was unsuccessful.
Usually not. Unless it was surgical procedure with metal clips used there will be nothing on x-ray to show venous ablation. The laser fibers and rfa technology used today do not leave anything radio plaque behind. You should give your doctor your full medical history as possible.
NO. X ray will not show where a venous closure procedure was performed in the leg. An ultrasound might. It is always a good idea to share your prior medical history and procedures with your physician.