My father is is in his late 50s and isn't very healthy he has near his knee veins protruding out they look very swollen?

Multiple options.: Varicose veins are due to leaking (refluxing) valves usually in the saphenous vein system. There is a gold standard of treatment and lesser ways to treat these veins. The gold standard is to have a venous reflux exam and laser closure of the leaking valves followed by microphlebectomies or sclerothrapy of the vv. Lesser treatments would be support hose and observation. See a vein specialist.

See a phlebologist: I see a lot of men with awful veins - including venous stasis and venous insufficiency - who say it doesn't bother them and so they're not going to get it fixed. What they don't know is this can cause chronic inflammation to the skin and lead to ulceration. Tell him to see a phlebologist or vein specialist.