Background Knee injuries are prevalent among air force pilots during military training, with anterior cruciate ligament (ACL) injuries being particularly common. ACL reconstruction (ACLR) is a well-established treatment for these injuries, but the timing of postoperative rehabilitation interventions is crucial for achieving functional recovery, returning to training and flight.

Objective To analyze the impact of the timing of postoperative rehabilitation interventions on the rehabilitation cycle, functional recovery, and the time taken returning to training and flight in pilots who underwent ACLR.

Methods Clinical data, rehabilitation treatment, general information, rehabilitation intervention time, rehabilitation evaluation (AROM, bilateral thigh circumference difference, VAS, Lysholm), rehabilitation therapies (cold therapy, neuromuscular electrical stimulation therapy, joint release surgery, neuromuscular control training, weight loss walking training, etc.), rehabilitation regression and air force medical evaluation of 4 military pilots who underwent rehabilitation at different time points after ACLR at the Department of Rehabilitation and Physiotherapy, Xijing Hospital, the Fourth Military Medical University, from March 2019 to December 2021 were retrospectively analyzed.

Results Case 1: On the 6th day of postoperative rehabilitation intervention, the patient experienced slight swelling and pain in the joints, without joint stiffness. With 3 weeks of rehabilitation, the patient achieved a knee AROM of 0°-125° on the affected side, with a bilateral difference in thigh circumference of 0.5 cm. The VAS score was 1, and the Lysholm score was 85. The medical evaluation deemed the patient fit to return to duty and resume flying at 6 months after surgery. Case 2: On the 14th day of postoperative rehabilitation intervention, the patient experienced joint swelling and pain, without joint stiffness. With 6 weeks of rehabilitation, the patient achieved a knee AROM of -2°-135° on the affected side, with a bilateral difference in thigh circumference of 1.5 cm. The VAS score was 0, and the Lysholm score was 90. The patient returned to work and resumed flying at 6 months after surgery. Case 3: On the 57th day after surgery, the patient started rehabilitation intervention. The patient experienced joint stiffness and limited flexion. With 13 weeks of rehabilitation, the patient achieved a knee AROM of -2°-130° on the affected side, with a bilateral difference in thigh circumference of 1.5 cm. The VAS score was 0, and the medical evaluation concluded that the patient was fit to return to work and resume flying with a Lysholm score of 91 at 8 months after surgery. Case 4: On the 89th day after surgery, the patient started postoperative rehabilitation intervention. The patient experienced knee stiffness and significant limitation in flexion and extension, resulting in a limp gait. After 17 weeks of rehabilitation treatment, the patient achieved a knee AROM of 0°-125° on the affected side, with a bilateral difference in thigh circumference of 2 cm. The VAS score was 1, and the Lysholm score was 86. The medical evaluation concluded that the patient was fit to return to work and resume flying at 9 months after surgery.

Conclusion Initiating rehabilitation as early as possible (within one week after surgery) leads to a shorter rehabilitation time needed to achieve a full knee range of motion and return to work and flying with a qualified medical evaluation. Early and standardized rehabilitation therapy can result in favorable rehabilitation outcomes and preventing joint stiffness, thus facilitating a quicker return to work and flying (within 3-6 weeks).