-osis. 1  1 suffix meaning a (specified) action, process, or result: homeosis, narcosis, zygosis. 2  2 suffix meaning increase in a pathological condition: calcicosis, psittacosis, varicosis. -osis. , pl. Combining form meaning a process, condition, or state, usually abnormal or diseased; production of an abnormal substance, increase of a normal substance, or parasitic infestation.
If non-surgical treatment fails to relieve the symptoms of accessory navicular syndrome, surgery may be appropriate. Surgery may involve removing the accessory bone, reshaping the area, and repairing the posterior tibial tendon to improve its function. This extra bone is not needed for normal foot function.
The navicular bone is the bone that sits just underneath the coffin and sort of acts os a pulley wheel for the ddft. When a horse is shod badly (almost exclusively a shoeing problem) the other structures in the foot get squashed, therefor forcing huge amounts of pressure on the navicular and the tendon and frog etc. A good sign is as the others have said but physical signs are visible to the eye.