All participants will perform a 6-week single-leg eccentric squat exercise. It will be performed on an incline board with a 25° incline. It will consist of a single-leg squat, with the downward component (eccentric phase) of the EEP performed using the symptomatic leg and the upward component (concentric phase) using the contralateral leg primarily. If pain occurs during the exercises, athletes will be asked to continue the exercise if they score ≤5 out of 10 on the Visual Acuity Scale (VAS). The exercises will be attempted in the first session of each week, and if no or very little pain is felt, the weight will be increased by 2.5% to increase the intensity of the exercise. Three sets of 15 repetitions per session will be performed twice a day. It will be performed 5 days a week. Participants will be asked to fill out an exercise diary (sets, repetitions, and daily frequency) and return it to the researchers at each follow-up session.

Age, gender, height, weight, BMI, sports age, occupation, dominant side, affected side, currently doing sports, did they do sports in the past

The pain intensity felt by the participants in the knee joint during rest and activity, respectively, will be assessed with VAS. VAS is an easy-to-use scale as it does not have any language and is frequently applied in clinics. Individuals will be asked to describe the pain they feel during the test on a 10 cm scale as "0" (no pain) and "10" (unbearable pain).

Assess symptom severity, knee function and sports ability in athletes with PT. VISA-P questionnaire consists of 8 questions. The first 6 questions are to assess symptom severity during sports activities and the last 2 questions ask about sports-related knowledge interaction and participation. The maximum score of the first 7 questions of VISA-P questionnaire is 10 points and the last question is 30 points. Theoretically, the maximum score of VISA-P questionnaire is 100 and the minimum score is 0. The maximum VISA score for an asymptomatic athlete is 100 points.

The Vertical Jump Test (vertical jump or upright jump) is a commonly performed fitness test to determine an athlete's leg muscle strength or explosive power. The higher the jump, the stronger an athlete's leg muscle/explosive power. The test will be performed with an Optojump.

The long-distance single-leg hop (SLHD) is the most frequently reported functional test. Participants will be instructed to stand on the leg to be tested, jump as far forward as possible, and land on the same leg. The test procedure will be explained and then demonstrated. Participants will be given a practice run before the main measurement until they become familiar with the test and will be performed three times on both legs, starting with the non-dominant leg. Participants must not have any loss of balance during landing before the jump distance is measured and recorded. Dropping the other foot during the jump or landing, any abnormal movement that causes the supporting leg to move during landing, or touching the ground with the upper extremities will be recorded as a failed attempt. After an unsuccessful attempt, participants will be reminded to maintain balance on the landing leg for two seconds. They will then be allowed to perform a new attempt. The jump test will be considere

Tegner activity scale (TAS) is a 1-item instrument that assesses activity levels for sports (competitive or recreational football, basketball, handball, etc.) and occupational activities (light or heavy work). It assesses the patient's work and sports activity level on an 11-level scale, with higher scores representing higher physical activity levels.