The voice of experience, I take it.
Yes of course.
I have on many occasions witnessed dogs becoming tied together immediately following mating.
I have myself on more than one occasion woken up to find my self somewhat glued to a female human counterpart.
The former is known to be caused by the swelling of the penis, while the latter is understood to be caused by the flaccidity of the penis in coincidence with the coagulation of vaginal fluids...
Although little understood by science in general, the baculum (penis bone) within the dog's penis is also thought to play a part in the act of knotting.
The bitch's vagina is also designed to clamp shut immediately following ejaculation- this is likely another evolutionary benefit resulting in the bitch's ability to hold (and not spill) semen.
This penis bone (baculum) is beneficial to the mating of many mammals (not humans) as it allows the penis to remain rigid at all times within the vagina, ensuring proper insertion.
But as you might imagine it can create a problem with the removal of the penis after the bitch's vagina has clamped shut.
p.s. On one occasion I walked outside the house to find my neighbor hosing down his two french bulldogs while they were knotted, but to no avail. He asked me if I knew what to do, and I told him to just be patient and they will eventually work themselves apart. Despite my warning, after 30 mins or so my neighbor became impatient and had his wife help him separate the dogs. He had her hold the male still while he violently jerked the female away. The screaming welp the male made when pulled apart forever left a scar on my eardrums and heart.
The bitch was obviously sore to walk for a few days to come, but I saw no sign of the male during that time. It was reported that he did little other than hunker down in bed and lick his junk.
Moral of the story is of course: NEVER pull dogs apart while knotted!