I have a LG LDF7810 WW. The bottom rack does not come clean any more. I pulled the sprayer arm and checked as manual suggested. Anything else?

it would be improbable that you put too tall an item on the top rack every time you wash, but it is also impossible to check without a see thru tub. Just make sure there are no tall items and maybe lower the top rack.
Some dishwashers have the top arm on the bottom of the rack and use a connection in the back when the rack is pushed in. If yours does make sure it isn't deformed and not making properly.

If the dishwasher won't clean dishes, check the lower wash arm assembly. If the lower wash arm isn't getting water, all of the dishes in the lower rack will come out dirty. Check to be sure the lower wash arm assembly spins freely. Also check to be sure the little holes in the lower wash arm aren't clogged or blocked.

I once had gunk in the rotating sprayer itself that was blocking things...is the dispenser opening properly? I reckon a thorough cleanse with a dishwasher cleaning detergent (the one that takes a super wash to do it) and check the sprayers...no joke a chicken bone was in one of them!!

Sprayers require water to pass through the jets to provide motion to the arms.

Suggestion;

Remove the sprayer from the machine and look for blockages. (Removal should be easy, at it is expected that the user will need to clean the jets occasionally; If you have any problems removing it, consult your manual).

try c.l.r. to clean dishwasher check and clean lower and upper spray arms out, run no detergent you can also run vinegar in it as well about a cup full,let the machine start to run then stop dish washer for a few hours then restart see if this works for you use a short cycle.

http://www.kitchenaid.com/assets/pdfs/product/ZUSECARE/8573754.pdf
I know this isnt the same model, they dont carry your manual as of yet. But it does have some suggestions to look at on page 17. I had the same problem and I looked really carefully and found my sprayer arm was blocked. I cleaned it out and havent had a problem with it again. I do check it regular now.

I had the same problem and fixed it by disassembling the lower spray arm and return filter, and cleaning all the junk out.
Most dishwashers have 'risers' that bring the water up to the top sprayer or arm located under the top rack. If the recirculating pump is plugged even a little there won't be enough volume or pressure to get the water up there.
Test this by putting a dry muffin pan in the top rack, flat, and running the dishwasher for a bit. If there is no water on the top (or the bottom) either the top sprayer or the sprayer arm underneath the top rack is not getting enough volume.
To fix this you need to clean out the screen and filter, where the water returns to be recirculated. If you don't have any confidence to remove the parts and clean it out yourself, get an appliance repair person to do the job.

This may help you.
I had the same problem and fixed it by disassembling the lower spray arm and return filter, and cleaning all the junk out.
Most dishwashers have 'risers' that bring the water up to the top sprayer or arm located under the top rack. If the recirculating pump is plugged even a little there won't be enough volume or pressure to get the water up there.
Test this by putting a dry muffin pan in the top rack, flat, and running the dishwasher for a bit. If there is no water on the top (or the bottom) either the top sprayer or the sprayer arm underneath the top rack is not getting enough volume.
To fix this you need to clean out the screen and filter, where the water returns to be recirculated. If you don't have any confidence to remove the parts and clean it out yourself, get an appliance repair person to do the job.

The sprayers are not powered but rely on the water pressure to spin them. If it's not spinning it could be
the spinner isn't engaging in the top rack as you slide it in
blocked jets on the spray arm
blocked feedpipe to the spray arm
faulty pump

Most dishwashers are fairly easy to dismantle to check the first few

Recommend you pull the bottom spray arm straight up, then out of the DW.
Remove 9 phillips screws that hold the filter shroud down. Remove the filter and clean/rinse it out.
While the filter it out, grab a flashlight and inspect all over the sump area. Especilly in the area the has the check valve that rotates (Vario motor-driven) to feed the water pressure either to the lower and then the upper arms. Watch out for broken glass! Also, inspect the impeller to see if it is undamaged and spins easily.
Reassemble, then test out.
If problems remain, the the wash pump motor is probably the culprit. Do you get any error messages on the time display?
Good Luck!