Light weight kit

[Bishop]

Suspended load backpack: Reduces impact loading through the knees when walking.
Don't know if anybody makes these commercially but for those mechanically minded then a DIY version could be worth a try.

 

[Graveworm]

I must add this is for hill walking and wild camping as opposed to bushcrafting in the woods. And walking for as long as my poorly knee will let me ;(

I think for that a Tent or bivvy and tarp works better than a Hammock. And what the others said, drop weight on yourself (good for knee too), shelter, pack and sleeping kit as that is where the biggest savings can be made on gear. I am sure you already have a pole or 2. Avoid carrying too much water by planning around several water rest stops (also knee friendly) and dried food is a no brainer. With the pack I would avoid silly lightweight for every day use and try to still keep some kind of frame as that will be better for your knees.

 

[Teepee]

I have the older GG Mariposa plus. Been using it for 5 years now very happily as my main backpacking pack. The new design looks much better than the old too.

I use it year round. It's just come back from it's third winter arctic trip where I used it as a cabin bag/day sack. I remove the pack stays and use a sit pad in the back which gives me 70l of capacity for around half a kilo. I find it comfy with up to 15kg which encompasses all my trips except full on winter trips with snowshoes/crampons/ice axe where a beefier pack is needed. I use socks other clothes in the pack straps to add more comfort and save more weight and bulk. I can manage a winter backpacking uk trip with it for 2 weeks including food.

The trade off to these pack is they need to be looked after. Always lift the pack on to your back with the hanging loops (good practice for any pack) and use a lightweight pack cover to protect against abrasion and keep the rain off the kit in the outside mesh.

To put it into perspective, my entire Mariposa weighs less than a quarter of the waist strap on my big SF Sabre.