Background. Hamstring muscle injuries are among the most common traumas occurring in athletes and football players. Thus, the rehabilitation time is crucial for their return to full athlete activity. Objective. Knee active range of motion deficit after the hamstring injury in futsal players correlates with rehabilitation time. The objective is to examine cases of hamstring structural injury in futsal players and find association between the Active Range of Motion (AROM) deficit and rehabilitation time. Methods. For this study, 200 futsal players with acute, first-time, unilateral posterior hamstring injuries were recruited, all men. All patients underwent clinical examination and ultrasonography. In 74 of 200 patients, sonography revealed no abnormalities in the musculoligamentary structures. Thereby, they were excluded from further investigation. Only 126 futsal players underwent the active range of motion testing. Injured areas were compared with the normal hamstrings in all athletes and with the control group. The AROM deficit was evaluated. The association between time to full recovery and the AROM deficit was identified. A control group (100 men) underwent examination in the same series of steps as the study group. Results. Biceps femoris was the most commonly injured muscle, making up 80% of injuries. The musculotendinous junction, proximal and distal, was involved in 91% of injury cases. Twelve athletes had an AROM deficit of 26 to 35 degrees. For them, the average length of the recovery period was 2.5 months at its minimum. Seventy or 55.5% of athletes had an AROM deficit less than 15 degrees. These athletes felt fully recovered after 3-4 weeks of rehabilitation. Conclusions: The active range of knee movement deficiency is an indicator that allows an objective prediction of rehabilitation time in futsal players.