*2.3. Follow-Up Assessment*

Assessment included Lysholm score, International Knee Documentation Committee (IKDC) Subjective Knee Form, Tegner activity level, and ACL-RSI scale. The Lysholm score is a 100-point maximum subjective questionnaire developed to evaluate knee functional status after ACL surgery [20]. The IKDC subjective score is a clinical questionnaire that assesses the functional status of the knee ranging from 0 to 100, with 100 indicating no limitations [21]. The Tegner activity scale is designed to grade patient's activity level based on work and sports activities from 0 (lowest level) to 10 [22]. ACL-RSI is a previously validated 12-item questionnaire that allows evaluating psychological readiness to return to sport following ACL injury or surgery on a scale from 0 to 100. The Italian version of the ACL-RSI used in the present study showed excellent internal consistency and reliability [18].

Jumping ability was assessed using a test battery modified from Gustavsson et al. [23], using the OptoGait (Microgate, Bolzano, Italy) system. This device allows us to calculate jumping height (in centimeters) from flight time (in milliseconds) measured by an infrared optical acquisition system connected to a software (OptoGait analysis software, version 3.22; Microgate).

Two types of bipodalic jumps were tested: squat jump (SJ), and countermovement jump (CMJ) (Figures 1 and 2). Then, monopodalic jumps were performed: CMJ, and side hop test (Figures 3 and 4). Each of them was performed with the uninjured limb first, followed by the injured. The SJ consisted of a vertical jump performed from a half-squat position with the knees flexed at 90◦. The CMJ was performed in the same fashion, with the exception that the starting position was an upright position, and the jump was performed after a quick sinking. Every jump was performed 3 times, and the average value was recorded. The side hop test consisted of performing as many jumps as possible during a period of 30 s between two parallel strips on the floor put at a distance of 30 cm without touching the strips (a maximum of 25% error was allowed; otherwise, the test was repeated). Limb Symmetry Index (LSI) was calculated as a percentage of test performance on the injured/operated limb compared to the contralateral limb.

**Figure 1.** Bipodalic squat jump.

**Figure 2.** Bipodalic countermovement jump.

**Figure 3.** Monopodalic countermovement jump.

**Figure 4.** Monopodalic side hop test.
