636 
NAVICULAR DISEASE. 
When the condition is preceded by bursitis, which Williams considers 
common, the parts are more or less reddened and injected, and the bursa 
is thickened and its surface roughened. Such disease must, of course, 
affect the tendons and navicular bone. 
Finally, inflammation may extend from the flexor perforans to the 
navicular bone ; Fambach, indeed, regards this as the rule. Isolated 
fasciculi of the tendon are ruptured by excessive strain, and the process 
commences. But the course of the disease, and especially its long 
period of development, contradict this view, though it is a fact that, 
with few exceptions, the tendons are always affected. Smith found 
disease of the tendon in 99 per cent, of cases. The portion of tendon 
in contact with the navicular bone at first shows brown-coloured spots, 
its surface loses its glistening cha¬ 
racter, and soon shows abrasion. 
Single fasciculi on the surface of the 
tendon become ruptured (fig. 250), 
partly torn away, and rolled upward. 
Microscopic examination shows them 
to have undergone fatty degenera¬ 
tion (Smith). In old cases the ten¬ 
dons may be extensively eroded, and 
may finally rupture. Almost all such 
changes in the tendons are, how¬ 
ever, secondary. Immediately the 
surface of the navicular bone be¬ 
comes rough from loss of the carti- 
Fig. 250. — Flexor pedis perforans tendon in. ^ _ „ • -i 
chronic navicular disease (after Brauell). a tubbing action, Similar to 
that between the articular surfaces 
in arthritis deformans, occurs between the rough navicular surface and 
the tendon. The fact that the portion of tendon most frequently 
affected is that exactly over the navicular bone supports this view, 
though granulation on the navicular bone may not be the sole cause 
of change in the tendons : rupture of fasciculi may perhaps at times 
be a primary condition, and seems indicated where the disease appears 
suddenly with severe lameness. Under favourable circumstances, and 
with long rest, union occurs between the perforans tendon and the 
navicular bone, being favoured by the granulations of the latter. The 
portions of tendon thus altered later become ossified. 
Causes. The tendency to navicular disease probably depends largely 
on peculiarities of conformation; hence the hereditary character of the 
disease, and its tendency to attack more than one foot at the same time. 
Smith seeks to explain the disease by referring it to faulty development 
of the bony tissue of the navicular bone. Theoretically nothing can be 
