The Effect of Cognitive-Based Neuromuscular Exercises on Reaction Time, Joint Position Sense, Proprioceptive Force Sense and Balance in Individuals Who Had Anterior Cruciate Ligament Surgery

Anterior Cruciate Ligament (ACL) injuries are among the most common knee injuries, occurring due to both contact and non-contact mechanisms, such as sudden deceleration, changes in direction, or landing after jumping, and leading to disruptions in knee stability and biomechanics. In the United States, it is estimated that there are between 100,000 and 200,000 cases annually, while the global incidence of ACL ruptures approaches 2 million cases per year. Treatment for ACL injuries can be either conservative or surgical. Conservative treatment is considered a viable option for specific populations, such as athletes who do not engage in activities requiring direction changes, individuals with no significant knee instability, and those with lower activity levels. ACL injuries result in quadriceps and hamstring weakness, reduced knee joint proprioception, and impaired balance.

To restore the anatomy and biomechanics of the knee, arthroscopic ACL reconstruction is performed to stabilize the knee and prevent secondary injuries, with approximately 30,000 procedures conducted annually in the United Kingdom. Although comprehensive rehabilitation is a critical component of ACL injury management, whether treated conservatively or surgically, there is currently no gold standard rehabilitation approach for such a widespread injury.

The type of rehabilitation protocol applied is one of the most significant factors influencing the outcomes of ACL reconstruction. Rehabilitation protocols have evolved substantially over the past few decades, with traditional rehabilitation, accelerated rehabilitation, and criterion-based rehabilitation protocols being the most commonly employed. These protocols aim to enhance muscle strength, improve proprioception, and ensure knee stabilization, with the timing and types of exercises determined by the biological healing and remodeling periods of the graft.

Criterion-based rehabilitation protocols, a relatively new approach, aim to provide patient-specific rehabilitation and maximize progress. Developed in 2016 by the Royal Dutch Society for Physical Therapy (KNGF), this protocol is divided into three phases: early, mid, and late stages. To progress to the next stage, patients must meet specific goals for each phase, which are verified through objective and subjective testing. The effectiveness and quality of early and mid-stage rehabilitation significantly influence long-term outcomes. The goals of early-stage rehabilitation, lasting approximately two months, include reducing effusion, restoring joint range of motion, and minimizing muscle atrophy. During the mid-stage, which extends from the second to the sixth month, the focus shifts to achieving full control of knee extension, restoring 80% of the muscle strength in the operated limb compared to the uninjured side, and regaining jumping ability. This phase includes exercises such as knee flexor and extensor strengthening, closed kinetic chain exercises, functional exercises, balance training, plyometric exercises, and neuromuscular exercises.

Neuromuscular control is essential for initiating movement and requires the integration of sensory information from proprioceptive, kinesthetic, visual, and vestibular sources, as well as cortical and spinal motor commands. This control is critical for the effective execution of movement. Recent studies indicate that ACL injuries are not isolated joint damages that merely affect stability and biomechanics but also directly influence neuromuscular control of the knee via mechanoreceptors located within the ACL. These injuries lead to neurophysiological effects on sensorimotor control. Following ACL injuries, these somatosensory changes may result in deficits in postural and motor control, leading to slower lower extremity reaction times. Additionally, nociceptive activity related to pain and swelling, combined with reduced joint position sense and kinesthesia, impairs movement quality. Neuromuscular control impairments, proprioceptive deficits, and disruptions in somatosensory inputs due to damaged mechanoreceptors may persist for 9-12 months, highlighting the need for targeted exercises during the mid-stage rehabilitation.