ANKLE-JOINT, ABNORMAL CONDI TION OF THE.—The deviations from the na tural or normal condition of the ankle-joint may be classed under those which are referable to accident and to disease : any defects which may be considered to result from congenital malformation shall be elsewere treated of. (See FooT.) Accidents.—The different structures which immediately compose the ankle-joint, as well as those which surround this articulation, and are merely accessary to its functions, are, each and all, liable to numerous accidents, the most important of which we shall here advert to.
These accidents may affect the tendons, the ligaments, or the bones.
Tendons.—Those tendons which pass behind the inner and outer malleoli are occasionally displaced ; and, although the accident must be considered a rare one, it ought not here be overlooked.
" The two peromi extensor muscles," says the late Mr. Wilson,l' "where they pass behind and below the fibula over a smooth lubricated surface of that bone, are bound to it by a strong ligament; but should the ligament give way, one or both of these tendons may escape from the groove or pulley in which they usually play, and being thrown forwards over the edge of the bone, in this new situation their action on the foot will be to bend it on the leg, when in their natural position it was to extend it. The peronwi having been habituated to act with the extensor muscles, continue to contract at the same time with them, but now they oppose the effect which formerly in conjunction with the extensor muscles they produced upon the foot, and by so doing excite much pain and irritation in addition to the lameness. When this situation of the tendon is discovered early, the tendon can be readily restored to its proper place, but if this is not done, it forms a new groove on the fore part of the bone, and the old one is filled up, or otherwise so altered that it cannot receive the tendon, and thus the pain and lameness may continue for life. I have seen this occurrence sometimes in the living body early enough to return the tendon, and have been consulted in cases where it could not be returned ; in one, where the pain was so violent that I recommended the divi sion and removal of part of the tendon ; the muscle then contracted to its full extent, and afterwards shrunk, and no inconvenience was felt after the operation. I have met with two or three instances of this kind of displacement of tendons in bodies brought into the dissect ing-room ; but of the previous history of the cases I could know nothing." Mr. Wilson
adds, " Those tendons which pass in grooves behind the inner ankle are liable to a similar displacement." Of the lattenaccident we have known but one instance, but of the former several.
Ligaments. — Accurate anatomical investi gations of the actual condition of the various structures which compose the ankle-joint, when affected by a sprain, have shown that in slight cases of sprain of this joint no thing unnatural has been discovered, as the bonds of union between the bones have been merely stretched or strained. In others more severe, the ligaments have been found broken or torn from their attachment to the bones, the synovial sac opened, and its fluid to have escaped from the cavity of the joint; the cel lular tissue around has been filled with extrava sated blood, and with synovial and serous fluids. In these cases the nerves, bloodvessels, ten dons, even the skin itself, have been subjected to a degree of stretching and extension, more or less considerable. Baron Dupuytren, from nu merous observations on the living subject, from post-mortem examinations, and experiments, is of opinion that a slight accidental torsion of the foot inwards or outwards, amounting to a sprain, only produces an injury, in which the ligaments are merely stretched ; but that a greater effort produces a separation of the lateral ligament from one or other of the mal leoli by laceration of its compact tissue, or of the periosteum which covers it, while the liga ments themselves remain unbroken. Oppor tunities do not often occur of discovering the effects of sprains on the joints by anato mical examination made at various periods after the accident ; but although Dupuytren's opinion may be correct as to the majority of cases, still others have found the lateral liga ments ruptured across, instead of having been torn from the bone. Mr. Wilson found, in a case where the patient died five days after a severe sprain of the ankle-joint, that the del toid ligament binding the tibia to the foot was lacerated, and that the synovial membrane of the ankle-joint was also much torn. In older cases he found evidences of chronic inflamma tion in the ligamentous structures around the joint ; that these structures were thickened and vascular, and had lost much of their plia bility.