My tendon had given out: stretched and ruptured beyond repair. A couple of doctors claimed that if I had received surgery on that tendon within a week of the rupture, it could have been returned to full service. Most people don't think to run off for foot surgery within days of a slight ankle or foot problem. The line between hypochondria and prudence varies a lot, but this is an extreme.
Besides, tendon insufficiency is very rare. Dr. Deland estimates that there are about 1,000 cases per year in the United States. This is roughly twice the rate of deaths by lightning in this country.
Some have observed that people who get it tend to be very flexible. This certainly fits: I've never had trouble sitting and holding the lotus position, and used to be able to put my feet behind my neck or kick the tops of door frames in college.
A British neurosurgeon I met on a tour in Australia asked if I had slipped a disk. In fact, I had, about a year before the tendon gave way, and the sciatica had appeared near the ankle that was later afflicted. He also asked what it's like to have a rare disorder. It's a little frustrating, since we don't know much about it.
It's not clear how one quantifies foot function, and then takes 90% of that. I took it to mean "Don't expect the foot to be fully functional ever again." There will be less flexibility, especially on uneven ground. Presumably, I won't be on the senior league volleyball or basketball teams, though there never was much chance of that any way. I'll be happy if I can walk and bicycle without problems.
The repair is clearly a kludge. It generally involves moving and repairing various tendons to balance the foot. This can require repeated operations. It also includes a calcaneal osteotomy. This involves cutting off the heel bone and moving it inward about 1cm, essentially catching and supporting the falling arch and ankle. The bone is fastened with a titanium screw, and sometimes a wedge of bone grafted from elsewhere is inserted as well. Sometimes another operation is required to remove the screw, if it gets in the way.
This procedure was proposed about 20 years ago, and has been used regularly for the past five years or so. We don't know how long it will work. If it doesn't work, the last-ditch effort is to fuse some of the outside foot bones, reducing the foot's flexibility and increasing the probability of osteoarthritis.
A lot of people inadvertently choose the first option. Since this condition is so widely miss-diagnosed, they have no choice. Eventually, the arch slowly collapses (valgus, the foot loses flexibility, and they end up walking on their ankles. I was nowhere near this stage.
The device approach does not appear to improve things much. If they do, things tend to get worse after they are removed. I gave much thought to this: it wouldn't be too bad to wear some sort of small ankle brace for the rest of my life.
The surgeons did not think much of this alternative. Of course, I was asking a barber if I needed a haircut. The same British neurologist warned me that there are an excess of American specialists, and European doctors often have to spend a great deal of time convincing American patients that they do not need surgery. (He hastened to add that his knowledge of my condition was dated and limited, and that the surgery could well be appropriate.)
Since we don't know what causes this condition, it's not clear what I can do to prevent it.