Ligaments
Ligaments transmit tensile forces across the joint, define the motion
limits of the bones with respect to each other and guide the relative movements
of bones within the motion limits. Their ultra structure is similar to that of
tendons, the principal difference being that they have a higher elastin content
which ensures that joint stability is not entirely rigid. The principles of
examination of an injured ligament can be applied to any joint that is readily
palpable by direct comparison with the uninjured limb:
grade
0 — normal ligament, normal joint
stability;
grade 1 — tenderness at the site of ligament
injury, no
detectable increase in joint laxity
whilst
`
loading the ligament;
grade 2 — increase in joint laxity but with
a solid
end point;
grade 3 — significant increase in joint laxity
with no end point.
Arthometers
have been developed to quantify the amount of joint laxity and are most commonly
used after cruciate ligament injury in the knee. However, as they only measure
the static stability and do not take into account the dynamic stabilisers of a
joint, the correlation between arthrometric estimation of joint stability and
the functional instability remains poor.
The
stability of joints varies enormously from one individual to the next. Women’s
joints tend to be more lax than men’s and all joints become stiffer as we grow
older. Connective tissue disorders such as Ehlers—Danlos syndrome or
Marfan’s syndrome should be excluded in patients with hyperlaxity. A patient
should be assessed for generalised ligamentous laxity using the criteria of
Wynne-Davies:
• elbow hyperextension;
• knee hyperextension;
• foot dorsiflexion of more than 45degree
• thumb can be bent back to touch volar forearm surface;
• fingers can be hyperextended to parallel forearm.
The principles of treatment for ligament
injuries are as for tendon injuries. However, ligament injuries are quite
commonly multiple, and because of their close proximity to joints the effect on
joint motion is more pronounced.