what-when-how
In Depth Tutorials and Information
widening of the space between adjacent toes. Patients often report that
they can no longer it into their existing footwear. Further to this, they may
complain of pain in the forefoot, often described as Morton's neuroma;
but in this case, rather than swelling of the interdigital nerve itself, it is
more likely that the swelling is causing compression on the nerve. The
presentation is the same, however, with sharp radiating pain which is
worse on weight bearing and is reproduced by pressure across the
metatarso-phalangeal joints. Additional problems in the foot may be Achil-
les bursitis, calcaneal spurs and rheumatoid nodules both in the heel pad
and other areas of pressure.
When walking, people with RA may present with altered gait. Stride
length can be shortened, particularly in patients with forefoot pain, and
as we know that stride length is an indicator of joint loading, this strategy
may be protective for symptoms and loading as a component of develop-
ing deformity. In addition to shortening stride length, people with painful
RA foot problems can be observed reducing speed and increasing
'double limb' support time, that is, increasing the time spent on two feet
rather than in the normal gait cycle, and ultimately developing a shuffling
gait once rigidity of the foot joints compounds this adaptation in gait.
There is some indication from early work by
Rome et al (2009)
that
patients with RA also have problems with postural stability. Patients in
this exploratory study displayed a significantly larger centre of pressure
excursion in the anterior-posterior direction during quiet standing when
compared with a non-rheumatoid arthritis control group, suggesting that
postural control mechanisms such as ankle strategies are impeded by
the disease process of RA.
Gait studies of AJC function in RA patients with long-standing disease
have shown kinematic dysfunction characterized by increased eversion
from heel strike through midstance, both in terms of magnitude and dura-
tion, and decreased inversion motion during the propulsive stage of
stance. This is associated with moderate to high levels of foot impairment
and associated disability. Furthermore, gait analysis detected subtle but
functionally important changes to the biomechanical function of the foot.
Assessment using 3D kinematics (reflective markers placed over land-
marks of the foot, tracked by cameras as the patient walks) of the AJC
aids evaluation of rearfoot function and could be used to identify those
individuals who would benefit from foot orthoses before irreversible joint
changes occur. It is difficult to measure simultaneously all the small joints
of the foot using 3D kinematics and they have to be grouped together
into functional units. As it is difficult to locate the markers because of
soft-tissue problems and the complex anatomy of the foot, it is essentially
reserved for use in research.
