Healthcare and Medicine Reference
Because the tendons run around a corner (allowed by
our rules in this case because of the clear fascial and
mechanical continuity), lubricating sheaths wrap around
the tendons to ease their movement under the retinacu-
lar strap (another example of the double-bag theory at
work - see Ch. 1 and Fig. 2.3).
Above the retinaculum, the SFL passes up the front of
the lower leg. On the lateral side, it contains the muscles
of the anterior compartment - the tibialis anterior and the
extensor digitorum and hallucis longus - in the scooped-
out shape anterior to the interosseous membrane. On the
medial side, we have found that, for best effect, the tissue
that overlies the tibia and its periosteum must also be
included (compare Fig. 4.10 to Fig. 2.1C, p. 64).
The fascial plane of the SFL passes up into the anterior
compartment of the lower leg, but on its way it passes
under the extensor retinaculum. The retinaculum is
essentially a thickening of an even more superficial
fascial plane, the deep investing fascia called the crural
fascia in the lower leg. This retinacular thickening is
necessary to hold the tendons down (otherwise the skin
would pop out between the toes and the middle of the
shin every time the muscles contracted - Fig. 4.9).
The anterior crural compartment
The tibialis anterior is generally the strongest muscle of
the anterior compartment, but the compartment as a
whole produces dorsiflexion and resists plantarflexion.
Here we deal with the two most common pattern prob-
lems in this compartment.
When the series of tendons from this compartment
pass under the restricting strap of the retinaculum, they
can get 'stuck' in terms of free movement. Presumably
the lubricating tunnels of the tendosynovial sheaths
adhere locally to the investing crural fascia above and
below the retinacula, owing to lack of full-range move-
ment use and being 'set' at a constant tension. Whatever
the cause, the solution is fairly simple and straightfor-
ward, and often produces surprised pleasure on the part
of the client due to increased ease of movement after just
a few passes.
Have your client supine, with the heels just off the
end of the table. Have her dorsiflex and plantarflex,
checking to see that she is tracking straight with the
ankle, so that the foot is headed directly toward the
knee, not up and in or up and out. You can add more
Fig. 4.9 The retinacula, which are thickenings in the deep
investing fascial layer called the crural fascia, provide a pulley to
hold in the tendons of the SFL and direct their force from the shin
muscle to the toes.
Fig. 4.10 The SFL occupies the anterior compartment of the leg, and the tissues on the front of the tibia (shinbone) as well. In (B), we
see how little of the leg is left when the SFL is removed. See also Figure 1.1C, where both these parts of the crural fascia have been
dissected as one piece - the anterior compartment and the surface fascia coating the tibia. Where holes appear in this fascia are
probably places where the person suffered trauma to the shin (as in falling upstairs), resulting in the crural fascia adhering to the
periosteum underneath. (DVD ref: Early Dissective Evidence).