Foot and Ankle-The ankle involvement is usually mild in RA but damage can occur in severe progressive forms of the disease.Clinical evidence for ankle involvement is cystic swelling anterior and posterior to malleoli. Of those affected with foot and ankle disease 90% have forefoot disease, 66% have subtalar involvement and 9 % have ankle disease.
Deformities of Forefoot: Hallus valgus deformity can be seen due to involvement of first MTP joints with medial displacement at the MTP joint and lateral deviation of the first toe.Actually this deformity starts with pathological changes in the ligamentous supporting structures on MTP joints resulting from the inflammation and later gradual progressive erosion ,remineralization and then blunt spur formation where the heads appear almost chewed due to advanced erosive diseae.This erosive disease along with giving away of ligaments lead to metatarsal spread and thus produce laterally deviated forfoot called as Fibular deviation.
This is the most frequently encountered rheumatoid foot deformities. Hallux valgus is defined when the first metatarsal and the base of fisrt phalange are at a angle greater than 20 degrees.As disease progresss first toe tends to lie under the second and third toe.Bunion usually get formed medially over metatarsal head. Irritable MTP joints are the main source of trouble. Due to planter callosities along the planter aspect of metatarsal heads patients feel as though there are pebbles in their shoes, On have to differentiate Rheumatoid Hallux Valgus from idiopathic type. Hallux rigidus or arthritis of first MTP joint leading to stiffness and inability to dorsiflex is seen in 13% females and 7% males.
Deformities of Midfoot: The midfoot is not commonly involved in RA but if it is than talonavicular and naviculocuniform joints are usually affected.As disease progress there occur involvement of muscle ,ligament supporting arches of foot, PesPlanovalgus is caused by involment of talonavicular joint resulting in pronation and eversion of foot.
Deformities of Hind Foot: Heel pain is uncommon in Ra.patients may complain ill defined heel pain when Tendoachilles insertion or planter aponeurosis insertion at calcanum is affected. Actually insertion of Tendoachilles become inflamed and thickened.
Rheumatoid nodule can develop in Achilles tendon at its insertion. Spontaneous rupture of tendon has been reported when diffuse granulomatous inflammation is present
8 Trieb.K.Management of the foot in rheumatoid arthritis J Bone joint surg Br 2005;87(9):1171-1177
8 Calabro JJ. A critical evaluation of the diagnostic features of the feet in rheumatoid arthritis Arthritis Rheum 1962;5 ; 19-29
8 Rask MR :Achilles tendon rupture owing to rheumatoid disease : case reportwith a nine year follow up JAMA 239:435-436,1978.