I know that some of the best training you can do to ride stronger is to simply ride more. I don't really do any strength training other than riding. I'd like to add some exercises in but under the following constraints:

1. They need to be knee friendly
2. I can do them at home (I only have ankleweights)

Thanks for your advice.

Well, if you have any way of adding weight to your body, like a weight vest or something similar, that will certainly help, but you can definitely accomplish a lot with just your body weight. Most lower body exercises are perfectly knee friendly, IF done properly. Forever, I thought squats were bad for the knees, then I learned to do them right, and ta-do, no more knee issues.

As for the exercises, I would focus on lunges, squats, and box jumps for leg specific workouts. Pick a distance, and do lunges, alternating legs, there and back. Increase the speed, distance, and number of times you go back and forth as you progress. As far as squats go, you can do multiple sets of body weight squats, or air squats, and see some impressive results. Once you are comfortable doing them, try doing a tabata workout (20 seconds all out, 10 seconds rest, repeat 8 times back to back). It's only a 4 minute workout, but trust me, you will be sore. For box jumps, simply find something sturdy at least 20 inches tall and jump from the ground, both legs at the same time, and then once your feet land on the box, stand ALL the way up. Jump or step down, and repeat. You can do the tabata intervals with these too.

The most important thing, especially for the squats, is to look up a few videos of good squat form.

https://www.youtube.com/watch?v=g1FpWEfJW1s

https://www.youtube.com/watch?v=iOdwETDQXCw

Here's a few good ones to get you started. When I started with the squats, there were two big things for me that made them knee friendly. First, getting the slight outward angle of your feet right. Second, realizing that you didn't really want to push with your quads, but rather with your glutes and hips. It's sort of hard to explain, but if you push through the center of your foot or the heel, the weight stays back further and you dive more with your hips/gluts. If you rock forward onto your toes, you start to rely more on your quads and you will feel more tension in your knees.

my surgeon says the worst thing for the knee is a deep knee bend with a twist - so stay away from that ... (squats are fine)

You can try lunges if you want, your knees are least stable at 90 degrees, and that's where lunges put you.

https://www.youtube.com/user/Performa...12/R7DBEjqNo8Y

I adapt the 1/2 squat by not leaning forward as much so it's more like pedaling out of the saddle.

https://www.youtube.com/user/Performa.../0/gztBydYNEMk

https://www.youtube.com/user/Performa...15/a4mJpgl0p2A

A bag of kitty litter makes a cheap25 pound weight. Once a week or so buy a rubber coated dumbell
at Walmart. They aren't expensive. Get a couple 5s and 10s to start.

Perform Better has these cool bands cheap, I use them a lot.
https://www.performbetter.com/SearchR...tegoryID_E_360

run up some hills

Tire drag

https://www.youtube.com/user/Performa...26/QrtF_ROgA_c

she's hot. I love fit women.