The Effect of Therapeutic Exercise on Cartilage Morphology and Physical Function for Individuals at High Risk of Knee Osteoarthritis

The Single Leg Hop Test for distance is one of four assessments used to evaluate athletes' horizontal movement capabilities. These tests, collectively known as the 4 Single Leg Hop Tests, were established by Noyes et al (7). They include the Triple Hop for distance, the Single Leg Hop Test for distance, the 6-meter hop for time, and the Crossover Hop for distance.

In the Single Leg Hop Test for distance, participants stand on one leg with their toes aligned along a designated landmark line. They then execute a forward hop, landing eccentrically while maintaining balance on the tested leg. The examiner measures the distance from the initial landmark line to the point where the participant's heel contacts the ground (8).

This test is valuable for assessing lower extremity strength, power, and balance. It has been shown to be a reliable and valid measure for evaluating aspects of lower extremity function (9-10).

The Single Leg Squat Test is a functional movement assessment used to evaluate lower extremity strength, neuromuscular control, and stability. Beyond its focus on lower limb function, it also helps identify core muscle strength and provides insights into an individual's capabilities in cutting, running, and landing (11). The SLST assesses the ability to alternate between concentric and eccentric contractions of the knee and hip muscles (12).

In the test, the patient stands on one leg with their foot aligned with a straight line. The examiner assists with balance and ensures proper form. The patient then performs knee bends until the line along their toes is no longer visible, within a 30-degree range of knee flexion. Each patient has 30 seconds to complete as many repetitions as possible, with the maximum number recorded (13-16). The physiotherapist monitors and adjusts the test to maintain accuracy and consistency.

The Timed Stair Climbing Test (SCT) is a functional performance assessment designed to evaluate lower extremity strength, endurance, and functional mobility. Participants will ascend and descend a 12-step staircase, with each step measuring 18 cm in height and 28 cm in depth. The objective is to complete the test as quickly as possible while ensuring a sense of safety and comfort. While the use of one handrail is optional, participants are encouraged to refrain from using it (17).

The Single Leg Chair Rise (SLCR) test evaluates quadriceps strength and can also help diagnose mid-lumbar nerve root impingement and radiculopathy (18,19). It has a sensitivity of 0.48, a specificity of 0.90, a positive likelihood ratio of 4.60, and a negative likelihood ratio of 0.58 (19).

The protocol uses a 45.7 cm chair. Participants, dressed and shod, sit with arms crossed, the tested leg flexed at 90 degrees, and the other leg extended without touching the ground. They rise to full knee extension and then return to the seated position to complete one repetition. The test includes two assessments: one measuring endurance with as many repetitions as possible in 30 seconds, and another measuring power by completing five repetitions as quickly as possible. Each test is performed twice, with the best score recorded (20).

To assess quadriceps muscle strength, the maximum voluntary isometric torque test will be performed using an isokinetic dynamometer (Biodex System 3 Pro). The procedure involves the participant seated with their ankle positioned in line with the dynamometer's axis at 60 degrees of knee flexion, secured by waist, thigh, and chest straps (21).

Before testing, participants will familiarize themselves with the process by performing isometric contractions at 50%, 75%, and 100% of their maximal effort. During the actual test, they will exert maximal force against the dynamometer's fixed arm for knee extension. Each participant will complete three trials with a two-minute rest between them, aiming to match or exceed a target torque displayed on a screen. The target torque will be adjusted based on their performance in previous trials. The maximum quadriceps muscle strength will be calculated using the recorded data (21).

The modified Bruce Test is designed for sedentary and elderly patients to estimate maximal oxygen consumption (VO2max) and assess aerobic endurance. Unlike the standard Bruce Test, which includes seven stages of increasing speed and incline on a treadmill, the modified version starts with a lower workload. It begins at 1.7 km/hr with a 0% incline and progresses to a 5% incline in the second stage, before resembling the first stage of the standard test. This modified approach includes "Stage Zero" and "1/2" to indicate the initial zero incline and a slight incline in the following stage, making it more suitable for less fit individuals (22,23).

VO2max measures the maximum amount of oxygen a person uses during intense exercise. It is calculated based on the duration of exercise using different formulas for men and women, without needing to measure inhaled and exhaled air directly (22,23):

Women: VO2max (ml/kg/min) = 4.38 × T - 3.9 Men: VO2max (ml/kg/min) = 2.94 × T + 7.65

The International Knee Documentation Committee Subjective Knee Form (IKDC) was developed in 2001 through a collaboration between the European Society for Sports Traumatology, Knee Surgery, and Arthroscopy, and the American Orthopaedic Society for Sports Medicine (AOSSM). This form is a widely used patient-reported outcome measure that assesses subjective aspects of a patient's health related to knee conditions. It includes domains such as symptoms, functional limitations, and sports activities. The IKDC has been translated into numerous languages, including Arabic for this study. It comprises ten questions, with one evaluating the impact of the knee on daily activities and nine focusing on performance. Scores range from 0 to 100, with higher scores indicating better health status (24).

The Knee Injury and Osteoarthritis Outcomes Score (KOOS) is a patient-reported outcome measure designed to assess the impact of knee injury or osteoarthritis on an individual's quality of life (25,26). It includes subscales for pain, symptoms, activities of daily living (ADL), quality of life, and recreational activities (25,26). Studies have shown that KOOS has superior psychometric characteristics compared to other measures. It has been translated into 40 languages, including an Arabic version for use in Saudi Arabia, which will be utilized in our study (27,28). KOOS comprises 42 items across five subscales: nine for pain, seven for symptoms, seventeen for ADL, five for sports and recreation function, and four for knee-related quality of life. Each item is scored from 0 to 4, with higher scores indicating better health status (29).