We have an apple tree that we inherited with our house that we bought 3 1/2 years ago. We haven't done anything with the tree, with the exception of a little pruning last year (more about that in a minute). A neighbor down the road from us told us that the previous owner of our house used to prune the tree himself, climbing up in it to do so.
I grew up around apple trees, so I know *a little* bit about pruning them. I know that they need some good mostly horizontal branches, rather than upright; lots of space between branches (not a plethora of branches); and that fewer branches will be stronger and will produce larger fruit.
I don't think the previous owner pruned this way--maybe more like you would an ornamental tree, just to keep the size under control. Last year sometime, maybe late winter or early spring, I started pruning it because it was getting so huge. I was just pruning it for size, not for production. I could only get maybe the bottom third of it from the ground. One of the pictures I'm attaching should show how much I did. I will get around to climbing it and pruning more. It is pretty big, but I think I can safely do it, a little at a time.
We actually thought the tree was a crab apple tree. Last fall it produced apples--we don't remember seeing any apples on it on previous years. The apples were very irregular shaped--knobby, bumpy, etc...and appeared to have bug/worm damage. There was one that was in pretty good condition, and I tasted it to see what kind of apple it was. It was actually pretty good--not a crab apple at all.
Now, there are no apples on the part I pruned (I can't remember if there were any there last year, but I haven't touched it since that first time I pruned over a year ago), but there are some up in the unpruned area. Again, they are irregular shaped, and buggy/wormy looking. The leaves have holes in them, and while I was taking pictures, I found a branch that had some sort of small, dark, slimy-looking growth or cocoon around it.
Here's my pics...I took them with my camera phone this evening, so they're not the best...I can get more pictures with my camera tomorrow.
First off, a disclaimer: I am by no means even close to an expert on fruit trees, and my advice is based on an experience growing up, so it may not be applicable to your situation.
That being said, I grew up with an apple tree that looks identical to yours. We had it for a few years, and then it developed the same type of damage that is presented in your pictures. I don't know what it was, but it sadly had to be removed. It might be a lost cause. Sorry.
Your tree probably isn't a lost cause at all, but it needs regular care. Apples are susceptible to several pests and diseases, and for practical purposes it's impossible to get edible fruit without some kind of spray program to address both sorts of problem.
The pictures are blurry, but at the least I can see that your apples have scab [a fungus disease] and codling moth damage. Lumpiness is likely from the apple maggot. But these can be addressed and the tree is in no danger from them.
What it will take is a good deal of work. The tree does definitely need pruning. Fungus disease likes an overgrown tree with minimal air circulation. Then you will need a sprayer capable of reaching the top branches of what looks like a full-sized tree.
First thing to do is pick up all the fallen fruit and dispose of it [not composting it], likewise the fallen leaves in the fall, as they harbor the spores that will infect the tree next year. Then begin a spray program when the tree is dormant. This is also a good time to prune.
Your state extension office can supply you with detailed guidance for spraying in your area.