Although the HADS was developed 20 years ago for the clinical measurement of anxiety and depression levels and was originally developed for hospitalized individuals, it now has a wide spectrum of use and can be used in many situations, including healthy people. Seven of the 14 items provide insight into the level of anxiety, while seven include questions about the level of depression. Each question is scored between 0 and 3, with a higher score indicating higher affect. Anxiety and depression sub-parameters are scored separately and a score of 11 and above is considered abnormal.

SF-36 scale will be used to determine the level of health status and quality of life of individuals.SF-36 is a patient-oriented assessment scale created in the United States of America that allows for general health screening.Each sub-parameter is scored between 0 and 100 points and a high score indicates good health status.The SF-36 scale has 8 sub-parameters including general health perception, physical function, social function, pain, mental health, role difficulties due to physical causes, role difficulties due to emotional causes and vitality and includes 11 questions with a total of 36 items.

The most commonly used disease-specific questionnaire for the assessment of disease severity in hip or knee OA is the WOMAC questionnaire recommended by the Outcome Measures in Rheumatology Clinical Trials. WOMAC assesses pain, endurance and physical functioning, functional status and stiffness. This scale has gained increasing acceptance in the assessment of OA since its introduction in 1986. The pain subscale includes five items asking about pain with activity, at rest and at night. The stiffness heading includes two questions. The functional status heading includes an assessment of difficulty in 17 different activities. The items are scored from 0 to 4 according to difficulty and the degree of pain and stiffness felt, with a higher total score indicating greater severity of the disease.

This scale, developed by Sullivan et al. (1995), measures the exaggerated negative mental reaction of individuals to current or anticipated painful experiences and the extent to which they catastrophize pain.The reliability and validity of the Turkish version of the scale was demonstrated by Uğurlu et al. (2017) and consists of 13 items.Each item is scored as never=0, slightly=1, moderately=2, greatly=3 and always=4.A high total score indicates a high degree of catastrophizing of pain.

This scale is a 17-question scale developed to measure fear of movement/reinjury.The scale includes parameters of injury/re-injury and fear-avoidance in work-related activities

The balance status of the individual is evaluated by getting up from a chair with back support, walking 3 meters at a normal walking speed and returning back to the chair and the time he/she sits on the chair is measured and recorded in seconds.The test is repeated 3 times.

In measuring the lower extremity strength and dynamic balance of the individual, the time to ascend and descend 10 steps of 16-20 cm stairs with a handrail as fast as possible is recorded in seconds. The test will be repeated 3 times and the times will be recorded.

To assess lower limb strength, the subject is asked to stand upright in a chair with arms crossed over the chest and then sit down again. The subject is asked to repeat as quickly as possible for a period of 30 seconds. The score for this assessment test is the number of times the individual stands up fully from a sitting position with arms crossed within 30 seconds.

The individual is asked to walk quickly but without running on a 10-meter path. Three repetitions of the assessment are recorded in seconds.

It will be used to assess the functional capacity of the patients. Patients will be asked to walk as long as possible in a 20-meter hospital corridor for 6 minutes in their own rhythm and with standard commands and the distance walked will be recorded in meters.

Muscle strength will be assessed using the Biodex System 3 Pro® isokinetic device (Biodex Medical Systems Inc., Shirley, NY, USA). Before the first assessment, participants will be recruited to a familiarization session. Each assessment will be preceded by a 10-minute warm-up walk and participants will perform knee flexor and extensor maximal concentric isokinetic muscle strength tests at angular velocities of 180°/s (10 repetitions) and 60°/s (5 repetitions) with a 30-second rest interval. Peak torque (PT) and average power (AP) will be recorded in Newtons (Nm) and watts (W) per meter.

In order to evaluate muscular endurance, it will be applied with 20 repetitions at 180°/s angular velocity. A rest period of 30 seconds will be given between the tests. Peak torque measurement will be recorded in Newton meters (Nm). Total work during all repetitions will be recorded in Joules (J).

To assess knee proprioception, "active position sense" will be measured at 30°, 45° and 60° by the "Biodex System Pro3 Isokinetic System (Biodex Corp. Shirley NY, USA) as recommended in the literature. Deviation from the target angle will be recorded as absolute angular error, regardless of whether the error is negative or positive. The test will be repeated three times. The mean of the patients' absolute angular errors at each test angle over 3 repetitions will be processed as data