Welcome! I am Dr. Altman, a licensed veterinarian and happy to answer your questions today.
May I ask what breed your dog is? Did your vet have any suspicions such as a cruciate or acl tear?
OK thank you
Just as when we wake up and begin moving our joints can be stiff, especially if your vet already suspects a cruciate injury
Doing passive range of motion after waking up can really help quite a bit
Also considering some physical therapy to build muscling in the leg and reduce the stiffness
Physical therapy, laser therapy, acupuncture are great alternatives to reduce the stiffness and give you a better handle on how to do passive range of motion and massage to loosen the joints and muscles
Yes, activity limiting the running, jumping, chasing balls, stairs, etc
Yes, x-rays definitely would be advised to get a diagnosis and a better idea how to proceed to control his discomfort
But I have several dogs that have had partial tears or discomfort respond well to laser therapy and postpone any further diagnostics or workup for a bit
I really would limit those if this is a partial tear of the cruciate these activities can cause a full tear and can also put him at risk of tearing his other knee (60% do within a year of the other knee)