**1. Introduction**

Aging is a progressive deterioration at the cellular, tissue and organ levels, resulting in a loss of homeostasis, a reduced ability to adapt to internal and/or external stimuli and an increased susceptibility to disease. Structural changes in various tissues are usually accompanied by negative changes in the functionality of all systems in the human body. With increasing age, there is an increased incidence of various diseases, which further accelerates disability and independence. One of the most frequent occurring causes of disability among older adults is osteoarthritis (OA), which commonly affects a knee due to high mechanical forces stressing the joint. When more conventional, i.e. nonsurgical treatments do not produce positive changes in physical function, pain relief and quality of life, the replacement of the degenerated and/or malformed joint is recommended for OA patients. Depending on the extent of the degenerated tissue, surgical replacement can be either total (e.g., when OA affects both compartments of the knee, TKA) or partial (e.g. when OA is limited to only one compartment of the knee; UKA). However, TKA is preferably performed as surgical treatment in almost 90% of all patients diagnosed with end-stage OA [1]. Since both, the incidence and prevalence of OA increase with age [2, 3], the longer life expectancy that is being faced globally will result in an increase of primary TKA rates which, by the year 2030, are anticipated to grow for more than 6 folds [4].

TKA has been shown as beneficial in improving physical function, pain relief and improving QoL of OA patients. However, despite using comprehensive surgical methods and post-operative rehabilitation approaches, the knee extensors muscle weakness persists over a long period, and might not achieve preoperative levels of the OA unaffected leg for up to 6 months post-surgery [5, 6]. Current rehabilitation practice after TKA consists of a more conventional approach to exercises that mechanically stresses the musculoskeletal system. Such exercise programs include joint mobility exercises to improve range of motion, gait relearning, weight-bearing exercises, neuromuscular function and proprioception training and strength and endurance exercises, using both voluntary and electrically triggered actions [7, 8]. A finding from a recent review and meta-analysis showed that outpatients professionally guided rehabilitation practice group had a consistently lower decline of the OAaffected knee extensors strength in the early periods following TKA when compared to usual care group. However, the authors suggested that strategies focused on preserving neural circuits of motor control must be considered for achieving optimal rehabilitation outcomes.

In the first days after TKA, patients are hardly physically active due to the pain caused by the surgical trauma. Therefore, inpatient rehabilitation is usually performed by passive exercises provided by physical therapists, continuous passive motion devices and transcutaneous electrical stimulation of the lower limb muscles. When overt movement is limited due to various factors (e.g. pain, opioids, cast, etc.), various cognitive strategies have been shown to be beneficial in improving neuromuscular function without mechanically stressing the muscles. One of the most studied strategies is motor imagery (MI). Recently, Paravlic and colleagues published the first systematic review paper with a meta-analysis that examined the effects of mental simulation strategies on physical function in TKA patients [9]. The authors showed a promising result favoring cognitive interventions over routine physical therapy alone, taking into account overall physical function, maximal strength of the affected leg, fast walking speed, timed up-to-go test and active knee joint flexion. Two other reviews were published in last 2 years that examined a similar question [10, 11]. These studies focused exclusively on MI practice only and included several different measures, such as range of motion of the affected knee joint and pain intensity. Currently, there is a substantial body of evidence regarding the effects of MI in the rehabilitation of TKA patients, warranting a collective assessment of their effects in the context of a review and representing a summary effect of MI in this specific patient population.

*Motor Imagery as Adjunct Therapy for Rehabilitation of Total Knee Arthroplasty Patients… DOI: http://dx.doi.org/10.5772/intechopen.106388*

The purpose of this study was to examine the effects of the MI practice intervention in TKA patients on several measures of physical function and pain intensity using the umbrella review.
