## 2 Case Report  
A 41-year-old, active male (177 cm; 74 kg) with no history of past musculoskeletal surgery complained of bilateral anterior knee pain (AKP) for the previous nine years. He had participated in various physical activities: swimming and soccer in middle school (20 months from the age of 13 to 14). In college, he majored in exercise science and played handball (46 months from the ages of 18 to 19 and 22 to 23). After graduating from college, he worked as a physical education teacher and physical activity instructor at a secondary school (24 months from the age of 24 to 25). Afterwards, he had been employed as an administrative assistant. As his new position was not physically demanding, he enjoyed running, weightlifting, tennis, badminton, and baseball in his free times (high intensity and frequency). When his AKP was tolerable (e.g., <3 out of 10 in numeric pain rating scale: NPRS) when attempting to run and jump, he had maintained a high volume of vigorous physical activity (>600 min per week). In addition to knee pain, the patient had a past medical history of taking Naproxen/Esomeprazole for a month due to low back pain at 37. The patient smoked for four years in his early 20s and consumed alcohol once or twice a month. No additional medical conditions were reported. One day, he felt severe right AKP (>5: NPRS) after playing tennis. The patient sought medical attention because of discomfort and swelling at the knee joint that impaired his daily activities. On initial presentation (performed by an orthopedic surgeon), there was no joint effusion (circumference on both sides: 32 cm measured at the inferior pole of the patella using a tape measure), and knee flexion range of motion (ROM) was within the normal limit (right: 131\({}^{\circ}\), left: 130\({}^{\circ}\); measured using a plastic goniometer). Manual muscle testing of knee extension [8] revealed right and left side strength of 4+/5 and 5/5, respectively. No neurological symptoms (sensation and reflex alterations) [9] were noted, and the special tests [10] related to the knee joint (Lachman's, anterior and posterior drawer, Apley compression/distraction, valgus/varus, and patellar grind test) were negative. After magnetic resonance imaging (Figure 1A,C: Discovery MR750, New York, NY, USA) was taken, bilateral chondromalacia (grade IV chondrosis) with plica syndrome (Figure 1B,D: ConMed Linvatec video system, Largo, FL, USA) was diagnosed. Two months after the initial evaluation, the patient underwent bilateral arthroscopic knee surgery. Chondromalactic of the medial aspect of the patella, trochlear groove of the femur, and thickened medial plica were first examined. Bilateral debridement was performed to remove articular cartilage from the patella and trochlear groove. Finally, resection of the medial synovial plica was completed using a motorized shaver and basket punch (ConMed Linvatec, Largo, FL, USA). The lateral retinaculum in the right knee was also removed (Figure 1E,F). One day after surgery, the patient began 12 weeks of intense exercise rehabilitation (Table 1 and Figures 2 and 3). Celecoxib was administered for postoperative pain relief. Three weeks later, at the patient's request, Naproxen/Esomeprazole was prescribed due to low back pain. At each rehabilitation session, the patient received 30 min of disinhibitory modalities (either two channels of sensory transcutaneous electrical nerve stimulation (TENS) [11], knee joint cooling [12] using an ice bag on the patella, or both) prior to performing resistance exercises for the previously suggested \"open, then exploit\" strategy [13]. When available, cold-water immersion (water temperature less than 20 \({}^{\circ}\)C; immersed up to the iliac crest) was applied for postexercise recovery. The external loads (kg) used for knee extension and leg press exercises were determined by the daily adjustable progressive repetitive exercise (DAPRE) technique [14]. Specifically, if the number of repetitions exceeded 7 in any set, working load was added (increments of 10 kg) at the next session.