First things first :
There isn't really such a thing as A "Rehab" Exercise.
There are only strength and conditioning exercises, which we use for rehabilitation purposes.
That said, some things get pigeonholed as 'rehabby'. And that's fine - they crop up a lot more often in rehab programs than as #bro-sesh #hypertrophy #gaainnzzzz clickbait on TNation.
However, the reason these exercises tend to appear so often in a rehab setting is precisely because they target a weakness or a physical need in a specific, safe and beneficial way. And they don't stop being beneficial once rehab is "complete".
Rehab is a lot like what they do at the zoo to get a hurt or sick animal back into its habitat. They treat the condition, keep it safe from further harm during recovery and try to nurture its own survival skills - so ideally when it gets back to the wild it can hunt on its own and look after itself without getting sick or hurt again. Just like zookeepers, when we release you into the wild after rehab, we want to see you getting back to your habitat healthy and happy - and staying that way.
Refining your movement and learning new movement skills during your rehab only to go back to the gym and do the exact same things you were before injury is the equivalent of that wild animal hanging around supermarket dumpsters to eat frozen party pies instead of fresh prey.
So these are just a few movements that I reckon should stick the transition out of rehab into everyday training programs.
BULGARIAN SPLIT SQUAT / REAR LEG ELEVATED SPLIT SQUAT
If I were going to a desert island and could only take one type of squat with me, I would pick Bulgarian Split Squats. WITHOUT HESITATION.
The rumour I first heard about them is that they came about at a time when Bulgarian weightlifters were taking extravagant amounts of PEDs and so were muscularly able to squat so heavy and so often that they were absolutely crushing their spines. So the split squat was created as a way to reduce the load on the spine in order to keep squatting huge volumes without grinding vertebrae into a fine paste. A quick Google search regarding that particular fable was unfruitful however I don't think we should let the truth get in the way of a good story here. Point is, if you can get enough stimulus through your legs and hips to create a strength adaptation WITHOUT overloading the spine, why would you not? Not to mention that it's one of a few squat variations that you can make into a glute-dominant movement. It also opens up the anterior hip with an active stretch of the flexors. And like all unilateral (one-sided) strength movements, you can use it to identify and rectify asymmetries.
So as an example of what I'm on about : if you were doing three sets of ten at bodyweight in a rehab program, then once you're pain-free and back in the gym on your own you could try sets of eight loaded up with some dumbbells or a kettlebell.
Plenty of athletes will move outrageous weights as a front-rack or back-rack barbell Bulgarian split squat. For hypertrophy or strength-endurance you can add pauses or half-reps or play with the tempo. If your sport requires explosive strength you could do jumping Bulgarians. That's the thing about these suckers - If you program right they will literally never stop being what you need.
Your calves are literally holding you up whenever you are standing, walking or running. They need and want strength and endurance. Also you can calf raise literally anywhere. If you do them right you don't even need to add weight to calf raises until you're like stupid crazy strong. FFS just do some raises.
MONSTER BAND / BANDED LATERAL WALK
The problem with these is everyone but bodybuilders seems to think they are just a pre-training activation exercise. Which is a shame because they are almost the only lateral-direction training a lot of us will do in the gym. 99% of strength training is in the saggital plane, or backward-forward movement. So if you train like that then you definitely need some variety, or if your sport requires side-to-side movement or change of direction then obviously you want to be strong laterally.
To turn them from activation into a strength exercise - just go further or add more bands to make them harder (without going into shit form) and/or reduce the glutes' recovery time by supersetting them another lower body exercise.
... should not be easy or boring. Like all "core" training, it's not something you should be able to do while talking, thinking about other things or breathing whenever you feel like it. Finishing a Pallof set with mild nausea and shakes is totally OK by me. When it starts to feel easier you can add reps or sets, increase band tension or time under tension, or try supersetting with something like resisted dead bugs, rollouts, hollow rocks, or dragon flags.
Similar to monster band walks - nearly all of traditional gym stuff trains the spine exclusively in braced extension. Jefferson curls are one of the only exercises that train loaded spinal flexion. Acclimatising the spine to move segmentally between flexion and extension is excellent for mobility, resilience and pain tolerance. If Jeffs worked for you during your rehab, I think it's a pretty good bet that they'll do your back a favour in your ongoing training. Just keep in mind this is more of a weighted mobiliser than a strength exercise - so defo progress the weight, but always keep it easy to move and focus on movement quality.
And that's just the first five that came off the top of my head - I'm sure there are heaps more and if you've got any to add, HMU in the comments.