162 
On the Sesamoids of the Knee- Joint 
the limb tendons (gastrocnemius, popliteus, plantaris) and ligaments (oblique 
popliteal, and short external lateral) all united to the sesamoid hold it m situ on the 
posterior surface of the external condyle, near, or on, or in rare cases projecting 
over the outer condylar border (pp. 46 — 71). 
The reader will recognise what an enormous stride the master-craftsman 
made in thus investigating the muscular attachments of the fahella lateralis in 
man ! Yet even to-day the anatomical text-books content themselves by de- 
scribing this sesamoid as occasionally occurring in the external head of M. gastro- 
cnemius, — a rough description as old as the mid 16th century — and suggesting as 
Galen did that, as a sesamoid, it is scarcely worthy of study. If we disregard, as we 
think we must, Gruber's theory of the purpose of the fahella lateralis and his identi- 
fication of the ci/amella with this sesamoid, we have still to trace the origin of these 
muscular attachments and the undoubtedly close relations of these two sesamoids. 
If we discard the first locus, i.e. the popliteal sulcus, which Gruber gives to the 
fahella lateralis in man, we find him recording two alternatives*. 
(i) Embedded in fibrous structures. The place of the embedment is the 
posterior wall of the knee-capsule where the tendon of M. gastrocnemius externus 
unites with the oblique popliteal ligament and with the origin of the short 
external lateral ligament or the partial union of some of these and the knee- 
capsule itself (pp. 39 — 40). 
(ii) In a facet or groove on the condylar articular surface generally near the 
border. This fticet is either flat or slightly concave, sometimes saddle-shaped f 
(p. 40). 
In the case of the fahella lying in a facet the base in contact with the facet 
has according to Gruber no cartilaginous covering. In the case of the fahellae of 
all mammals — Gulo vittalus excepted — the base where they articulate has a car- 
tilaginous covering (p. 71). 
Accordingly it will be seen that it is hardly accurate to say of the fahella and the 
cyamella that the former is found in the tendon of M. gastrocnemius and the latter 
in the tendon of M. pojditeus. It is more accurate to assert that the latter will be 
found in the popliteal sulcus, and the former on the posterior articular surface of 
the condyle, either somewhat removed from it, or in the close contact of a facet. 
The muscular attachments of both are found to be in part closely similar. Thus 
Gruber's error in failing to distinguish between the fahella and cyaviella in man, 
* It is singular how very closely Gruber's description of the sesamoid of the popliteal sulcus (our 
cyamella) agrees in its muscular attachments with those of the fahella lateralis in its embedment locus. 
Thus he writes : referring to Fig. No. 4 of his Tafel (see our Plate V, Fig. 10) " Das ossiculum und die 
Cartihuio liegen im Sulcus jjopliteus externus von fibrosen Gebilden (a, b, d [i.e. Knee capsule, oblique 
popliteal ligament and short external lateral ligament]) mit welchen sie verwachsen sind, und von 
Muskelbiiudeln (k, 1, [i.e. M. gastrocnemius externus, M. 2^lantaris]) welche von ihnen eutspringen 
umlagert." It will be seen that when both sesamoids are not simultaneously present — as they are in 
the case of the cat which has both lateral fabella and lateral cyamtlla, — there is some reason for con- 
fusing the two. 
\ A flat facet occurs in ^ of such cases, a really deep groove is very infrequent (p. 41). 
