Background: Pain and weakening of muscle strength are the most important problems in orthopedic patients. Isometric movements are effective in reducing these problems. Due to the lack of studies in this field, this study was conducted with the aim of investigating the effect of isometric movements on pain control and muscle strength reversal of lower limb fractures. Methods: This clinical trial was carried out in 120 patients aged 15 -49 years suffering from lower limb fracture admitted to the Shahid Beheshti hospital of Sabzevar in 2016 with random allocation to intervention and control groups. In the intervention group, physiotherapy was performed by isometric movements four hours after the surgery and then, up to five consecutive days, each day four times of half an hour. The amount of pain and reversing muscle strength was investigated before and after the intervention in both groups. STATA 11 software was used to analyze the data at a significance level of 0.05. Results: In the intervention and control groups, there were 83% and 85% males, 17%, and 15% females, respectively. The age groups of 40 -49 years (37%) and 30 -39 years (35%) were the most frequent. The Wilcoxon test showed a significant difference between the amount of pain before (6.86 ± 1.18) and after (2.86 ± 1.89) the intervention (P < 0.001). Fischer's exact test showed a significant difference between the groups in terms of muscle strength after the intervention (P < 0.001). Conclusions: Isometric movements exercise is the most effective method for relieving pain and reversing muscle strength, which can be recommended by orthopedic doctors because it facilitates recovery and accelerates the return to normal life.