I did a finisher earlier this week that's so simple. Feel free to steal it...

• 1-Arm Kettlebell or Dumbbell Swings (10/side)
• Rest 20 secs 

Repeat for 10 rounds (use a lighter weight since you're doing so many rounds). If you're new to this kind of thing, stick with just 4-5 rounds and build from there. 

These are a great way to work your lower body and core without pounding your knees.

Speaking of which, I've heard a lot of people over the years say they can't stay active because their knees hurt too much. 

Many folks bring it upon themselves by making these crucial mistakes when exercising, causing long-term damage to their knees.
 
#1 "Locking Out" When Doing Leg Presses, etc.
 
This is when you do a Leg Press, fully extending your legs until your knees "lock out" before doing another rep. This puts unnecessary stress on your knee joint. So when pressing, go about 95%, just before your knees "lock out". 
 
#2 "Forcing" Squats, Lunges, etc.
 
This is when your knees are in pain, yet you think you can fight through it. That's just dumb and you can be doing a lot of serious damage to your cartilage, etc. The "No pain, no gain" mentality is absolutely stupid. Don't fall for it. 
 
Sub these moves for knee-friendly exercises such as glute bridges and 1-leg glute bridges. Step-ups are a great way to progress from the bridges. Simply step up onto a box or bench and take a solid 3 seconds to lower yourself. 
 
And if you're experiencing any kind of knee pain, don't "mask" it with Ibuprofen or creams. It's time to get to the root of the problem using natural techniques.
 
And no, it's not foam rolling, either. 
 
It's this simple 5-minute knee pain hack found here.
 
To a pain-free life,

Mikey