Gastrocnemius Contracture in Patients with Rheumatoid Arthritis
INTRODUCTION: Rheumatoid arthritis is a chronic disease affecting multiple joints of the body. More than 90% of patients affected by rheumatoid arthritis develop foot or ankle pain over the course of the disease. Prior studies in non-rheumatoid patients have demonstrated an association between an isolated gastrocnemius contracture (lack of ankle dorsiflexion) and foot and ankle pain. To date, no study has measured ankle range of motion in rheumatoid arthritis patients in a validated manner. The purpose of the current study is to report ankle dorsiflexion in rheumatoid arthritis patients as well as a control group utilizing a validated measurement instrument. Our hypothesis was that patients with rheumatoid arthritis would have similar measured ankle range of motion to controls. METHODS: Institutional review board approval was obtained and a prospective case-control study was performed. We utilized a previously validated device to measure ankle range motion and isolated gastrocnemius contracture in 73 patients diagnosed with rheumatoid arthritis as well as 73 controls. The measurements were repeated three times with the knee extended to isolate the effect of the gastrocnemius muscle. We additionally performed a clinical examination and goniometer measurement of ankle range of motion. Patient history, severity of rheumatism, and demographics were also obtained. RESULTS: The rheumatoid arthritis group had a mean dorsiflexion of 12.5 degrees compared to a mean of 18.6 degrees in the control group with the knee extended, a statistically significant difference (p< 0.05). The device was used three times on each patient with no significant difference between measurements, (p>0.05). The difference in dorsiflexion was significantly less utilizing a goniometer than using the validated device, which may be due to measurement technique and external landmarks (p<0.05). CONCLUSION: Patients with rheumatoid arthritis had less ankle dorsiflexion than the control group with the knee extended. This is the first, and largest, study investigating ankle range of motion in patients with rheumatoid arthritis utilizing a validated measurement device as well as a control group. The clinical significance of this study is that it provides evidence that patients with rheumatoid arthritis have decreased ankle dorsiflexion despite a lack of foot and ankle pain. In light of the high lifetime incidence of foot and ankle pain in the rheumatoid arthritis population and previous studies which demonstrate decreased ankle dorsiflexion in patients with foot and ankle pain, this study provides some evidence that the decreased ankle dorsiflexion may be a contributing factor in foot and ankle pain, but further studies are needed.