Rheumatoid arthritis is a systemic disease that causes chronic inflammation of the synovial membrane of joints and tendons.
Patients suffering from this condition can develop significant deformities of the foot because of the gradual degeneration of the joints over time.
This pathologic process commences with the onset of synovial fibroblast hyperplasia; the synovium in rheumatoid arthritis undergoes a major transformation with the sublining region showing accumulated perivascular lymphoid nodules and the intimal lining showing a marked increase in cellularity.
This is caused by an increase in type A macrophage-like cells and type B fibroblast-like cells. These, in turn, activate the secretion of chemokines and inflammatory cytokins such as interleukin 1 (IL-1) and tumour necrosis factor alpha (TNF-alpha).
These cytokins activate the production of fibroblast-like synoviocytes and mensenchymal cells, which are responsible for the production of enzymes called metalloproteases, leading to a degradation of the extracellular matrix.
This occurs in conjunction with the formation of pannus, made up of macrophages, osteoclasts and invasive fibroblast-like synoviocytes, at the cartilage-bone interface which facilitates bone and cartilage destruction.
Foot deformities such as hammertoes and hallux valgus, are secondary manifestations of this type of chronic synovitis, which causes erosion of the medial capsule of the first metatarsophalangeal joint and the metatarsal head surface.
The functional integrity of the hallux is compromised in the process; with a decrease in the weight bearing capacity of the hallux, higher constraints are placed on the other metatarsophalangeal joints.
There is also an eventual rupture of the collateral ligament and the plantar plates, leading to a dorsal migration of the plantar aponeurosis from the transverse rotation axis of the metatarsophalangeal joints; this contributes to extension and dorsal dislocation of the proximal phalanges of the digits.
The high incidences of foot damage related to rheumatoid arthritis make the formulation of early evaluation and treatment strategies essential for the protection of foot joints.
One of the conservative measures of managing rheumatoid arthritis of the feet involves offloading of shearing forces from the forefoot and stabilising the hind-foot through the use of supportive foot devices which reduce pain and optimise plantar pressure in the metatarsals.
By normalising gait patterns and eliminating abnormal movements of the foot such as hyperpronation, patients with rheumatoid arthritis have a better defence from developing foot deformities which can significantly inhibit their walking capabilities.
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