Posterior Tibial Tendon Dysfunction in Rheumatoid Arthritis

Although hindfoot pathology in rheumatoid arthritis is a significant cause of disability for patients, the etiology of the planovalgus deformity is controversial. The present study surveys 99 patients with clinically proven rheumatoid arthritis for the presence and severity of hindfoot pathology. Specific attention was directed at the function of the posterior tibial tendon, as disruption of this structure has been implicated by some investigators as a cause of hindfoot deformity in rheumatoid arthritis. Assessment of posterior tibial function was by manual testing using two different grading scales, as well as by examination for several signs associated with posterior tibial tendon dysfunction. Between 13% and 64% of the study population could be considered to have posterior tibial tendon dysfunction, depending upon the specific diagnostic criteria used. Using the presence of all three of the most stringent criteria for diagnosis, 11% of patients were believed to have posterior tibial tendon dysfunction. These criteria were loss of the longitudinal arch, inability to perform a heel-rise, and lack of a palpable posterior tibial tendon. This study demonstrates that planovalgus deformity in rheumatoid arthritis can be due to clinically evident dysfunction of the posterior tibial muscle-tendon unit. There is a complex interplay between hindfoot joint disruption due to the inflammatory process and deformity due to tendinous dysfunction. If there is primary subtalar joint instability secondary to the inflammatory process, the posterior tibial tendon is rendered dysfunctional due to deranged hindfoot mechanics, as with primary posterior tibial tendon rupture. Since treatment of either condition (i.e., primary hindfoot instability or primary posterior tibial tendon rupture) is similar, the distinction is not important clinically. What is important is that attention to the specific cause of planovalgus would be expected to improve the overall treatment of rheumatoid feet.