Arthrokinematic movements in the knee joint are performed naturally, which indicates the stability of this joint, it is provided by the shape of the condyles, menisci, and patio support structures, the most important of which are the four main ligaments of the knee [1]. Among the mentioned structures, the Anterior Cruciate Ligament (ACL) plays a key role in knee stability [2]. Recent research has shown that the prevalence of ACL injury in individuals between the ages of 10 and 14 is increasing rapidly [4]. One of the first and most important consequences of this injury in the joint is the possibility of osteoarthritis in the knee joint [5]. Due to the pivotal role of this ligament in controlling the stability of the knee joint [22], it has been proven that its rupture will lead to a decrease in sense of depth, balance, decreased strength, decreased muscle function, and biomechanical changes [23]. Past studies have shown that even a damaged ACL that has been rebuilt shows signs of instability [21-26]. 
According to Barinius et al. (2014), after reconstruction of the ACL, 57% of those who were monitored for 14 years they had developed osteoarthritis in the injured knee [26]. The above raises the question of what arthrokinematic changes occur after ACL rupture and even after reconstruction, which causes irreversible complications? Therefore, the present review aimed to identify the most important arthrokinematic changes before and after ACL reconstruction as well as after a rehabilitation period according to previous research.

In this review article, we tried to collect the studies on arthrokinematic changes of the knee with ACL injury before and after reconstruction compared to a healthy knee from 1970 to 2020. These articles were done by searching the websites of Ebsco, Scopus, PEDro, Webof Science, Google Scholar, PubMed, Science Direct, CINAHL, SPORTDiscus, EMBASE and MEDLINE. The keywords used in this search included the following and their synonyms:
Knee, Gait knee kinematics, Gait knee kinematics Injured, Anterior cruciate ligament deficient, Arthrokinematic, Sagittal Plane Knee Motion, Anterior Cruciate Ligaments, Knee Joint Movements, Knee Pathology, ACL reconstruction Knee hypermobility, Accessory movement.
Manual search was also used to find articles. In this study, the quality of articles was also scored with the Modified Downs and Black checklist [27]. In fact, this checklist is set up to evaluate the methodology of random and non-random articles, based on this checklist, articles are divided into four levels. If the article score was between 24 and 28, the level was excellent, 19 to 23 was good, 14 to 18 was relatively good and less than 13 articles was considered poor.

According to the search method, 127 articles were found and at the end, 20 articles were reviewed and finalized according to the inclusion and exit criteria. 8 studies evaluated knee arthrokinematic when walking and running normally or downhill on the treadmill [26-36]. Seven studies examined arthrokinematic of the knee in static position and weight bearing on one leg [37-43]. Tow studies on going up and down stairs [44-46], one study was performed on a trampoline [47], another was performed on Lachman test [48], and the remaining study performed an arthrokinematic evaluation of the knee joint on a corpse after rupture [49].
Among the studies, 15 of the 20 found that the injured knee’s anterior glide was significantly increased compared to the healthy knee. However, this arthrokinematic change was greater in the internal epicondyle than in the external one than in healthy individuals. After the anterior glide, the second and third obvious arthrokinematic changes that occurred between the two groups were an increase in the internal glide and an external rotation, respectively. Among the articles, it is agreed that the most common arthrokinematic difference observed in injured individuals compared to healthy individuals occurred between 15 degrees of flexion and full knee extension. Finally, research results indicate that the arthrokinematic of the knee after reconstruction were more similar to those before than to a healthy knee, also, the arthrokinematic movements of the reconstructed ligament, even after a period of rehabilitation, were more similar to the non-reconstructed knee than to the healthy knee.

The highest arthrokinematic difference was observed in injured individuals compared to healthy individuals in the anterior glide and at angles between 15 degrees of flexion and full extension of the knee [29, 38, 40, 42, 49, 50]. Hoshino et al. (2012), Douglas et al. (2005) as well as Sangboom et al. (2015) have noted that changes in the anterior glide occur more frequently in the internal epicondyle than in the external epicondyle in people with ACL injury than in healthy individuals [32, 41, 48]. Research has shown that the injured knee has more external rotation or the internal rotation has decreased significantly than the healthy knee in certain movements [37, 38, 43, 46, 48]. It is also important to note that the results of the research showed that there was no significant difference in the arthrokinematic changes that occurred before and after the ACL reconstruction. The last and perhaps one of the most important points about people with ACL rupture that is very important and unfortunately less considered is finding the internal tibial glide in these people [32, 35, 36, 45].
Hoshino et al. (2012) have concluded that even after a period of rehabilitation people who had rebuilt their ACL, in the heel strike stage while running downhill, compared to healthy individuals, they had more roll and glide movements in the knee joint [32]. Ga O Bo et al. (2010) also prescribed a 6-step rehabilitation course for these individuals. The results of this study showed that the kinematic variables of a reconstructed knee, despite participating in a rehabilitation program, are more similar to a non-reconstructed injured knee than a healthy knee [46].

This study is a systematic review and there is no need to for ethical approval.

This research did not receive any grant from funding agencies in the public, commercial, or profit-non sectors.

Conceptualization, methodology and supervision: all authors; Review and writing the original draft and sources: Mostafa Payandeh, Zaher Mohammad Ashour; Review and editing: Ali Asghar Norasteh.

The authors declared no conflict of interest.

The authors would like to thank the Research And Educational Officials of the University of Guilan and the Faculty of Physical Education and Sports Sciences.