Perhaps the biggest problem that people experience in the initial period when coming back from an achilles tendon rupture is the oftentimes significant calf muscle atrophy (reduction) in the injured leg due to it being out of use for so long when in the cast and long boot. It is quite amazing to see the difference in appearance in both legs when you get out of the long boot and first start walking again.
I saw around a 1.5 inch reduction in my right calf muscle circumference at its thickest part when I first came out of my long boot and started walking. Even two years later, my right calf muscle circumference is still around 0.9 inches smaller than my left calf muscle circumference at the thickest part (around 15 inches in the good lack versus 14 inches in the damaged leg). However, I have been a bit lazy in doing calf exercises, and I never got physical therapy when I first came out of my boot and started walking.
Around 1.5 years post injury, I did go for 4-5 physical therapy sessions to try to get my calf muscle to grow back, but I wish I had done this sooner. My advice: go for physical therapy right away if you can afford it! Also note that I had a re-rupture of my achilles tendon soon after I first came out of the boot, so my calf muscle was disabled and out of use twice within a span of a few months. For more, see my achilles tendon rupture story.
— Australia football player Nathan Foley saw significant calf muscle atrophy after his achilles tendon rupture in 2012. Here is an article with video of his recovery and photo of his atrophied calf muscle towards the bottom of that link.
— “Tomtom” on achillesblog has great documentation with many photos going back almost 4 years, and his biggest recent problem has been the weak calf muscle strength. He also had to have an achilles tendon shortening surgery.
— “Hoss” on achillesblog in his one year update post states that “Even now my left calf (14.5 inches) is a little more than 1/2 an inch smaller than my right (15.15 inches)”.
— Kris has a great page on his site where he discusses his own atrophied calf muscle that has never regrown fully even years after the original injury.
— A good article from August 2014 on return of strength after an achilles tendon rupture, with some discussion on calf muscle recovery.
— The famous actor and wrestler Dwayne “The Rock” Johnson ruptured one of his achilles tendons some years ago, but I could not find any information on the web of which leg he ruptured. From the looks of this photo of him exercising, it seems like his left calf muscle is significantly smaller than his right calf muscle. Therefore, I would guess that he ruptured his left achilles tendon.
There are some studies that suggest that calf muscle atrophy is slightly less after surgical treatment versus non-surgical treatment, although other studies suggest no difference. Even for those who get successful surgery and excellent and timely physical therapy, in many cases a calf muscle never grows back to its original volume. At the same time, I have heard of many people who did get a close to full recovery in calf size after injury. Perhaps genetics and diet also play a part in the final outcome.