The correlation between chronic ankle instability and strength deficit of the hip and knee

. Introduction: The aim of the present study is to analyze the correlation between people that suffer from chronic ankle instability and muscle strength deficits of the proximal joints of the lower limb, which are the hip and knee. Methods: The narrative review was conducted on MEDLINE using the selected keywords to build the search string. After inclusion and exclusion criteria were applied, the articles were independently screened by two authors reading the titles and abstracts or full articles. The quality assessment was conducted using the NIH quality assessment tool for observational cohort and cross-sectional studies, the methodological index for non-randomized studies scale, the risk-of-bias tool for non-randomized trials, and the Critical Appraisal Skills Programme checklist. Result: From 506 papers originally identified through database search, six studies were finally selected. The quality score was medium to low in all studies according to selected tool. Major of the included studies underlined that the lower limb strength deficits represent a key factor in the rehabilitation path in patients with chronic ankle instability (CAI) and, in addition to predictable ankle’s muscle impairments, hip strength was a significant weakness in performance evaluation in this type of patients. Conclusion: It’s not possible to confirm to our knowledge a strictly significant correlation between strength deficit of hip and knee, when appreciated. These results, however, might suggest another time that the difference between people who suffer from CAI and coper is the rehabilitation program that patients follow after an injury.

Several factors contribute to chronic ankle instability, such as impaired dynamic balance, increased peroneal reaction time, and decrease eversion strength, compared with controls (de-la-Morena et al., 2015;Thompson et al., 2018;Barra et al., 2021).
A recent systematic review (Dejong, Koldenhoven, & Hertel, 2020) on CAI and proximal alterations and adaptations of the trunk, hip, thigh, and knee, concludes that there is currently no synthesized information for neuromuscular and biomechanical outcomes during strength, balance, jumping, and running (Bezerra, Vale, Brandão, Pernambuco, & Dantas, 2022;Flores-Leon, Leyton Quezada, Martínez Hernández, Salazar Reinoso, & Berral de la Rosa, 2022).However, they found triplanar hip strength deficits and altered knee flexion angles during jumping evaluations.Khalaj et al. found strength deficits in ankle inversion and eversion, as well as differences in hip and knee strength between individuals with CAI and controls (Khalaj, Vicenzino, Heales, & Smith, 2020).These authors point out that strength deficits measured statically are important, as weakness can negatively affect performance in tasks with increasing demand and contribute to functional impairments during dynamic movement.Donovan et al. developed a clinical trial through which they wanted to determine whether a 4-week rehabilitation program that included destabilization devices obtained greater effects on self-reported function, range of motion, strength, and balance than rehabilitation without devices in patients with CAI (Donovan et al., 2016).As in other research conducted to improve injuries in other joints (Cuenca-Zaldívar, Acevedo, Caballero-Nahúm, & Fernández-Carnero, 2021).There are few published studies examining the trunk and aiming to identify differences between CAI and healthy groups (Orellana et al., 2022).
Accordingly, this review aim to analyze the correlation between people that suffer from chronic ankle instability and muscle strength deficits of the proximal joints of the lower limb, which are the hip and knee.

Methods
This is a systematic literature review of studies investigating or reporting an association between lower limb joint strength and overall stability in patients with chronic ankle instability.PRISMA guidelines were followed during the design, search and reporting stages of this systematic review.The protocol for this systematic review was registered on PROSPERO.
Additional records were searched through other sources to complement the database findings (manual search of reference lists).Two authors (A.B and J.B.) performed the search and evaluated the abstracts independently for potential eligibility and subsequently full-text publications for eligibility.A third author (J.H.V.) resolved discrepancies (Villafane, 2022).Each researcher reviewed the title and abstract of all the articles, selecting the relevant ones according to inclusion and exclusion criteria.

Eligibility criteria
The types of studies included were: cross-sectional studies, quasi-experimental studies, and case-control studies, with restrictions regarding the English language and not regarding the date of publication.We excluded all repeated articles, case reports, letters to the editor, pilot studies, editorials, technical notes, review articles from analysis, and articles written in any other language than English.
• Population: The participants in the selected studies had to be adults (≥18 years old age) with a diagnosis of chronic ankle instability (Hertel & Corbett, 2019).• Intervention: Hip and knee strength assessment

Selection of studies
The search was performed independently by two authors (J.B. and A.B.).The titles were evaluated blindly for potential eligibility, and then the abstracts of articles were retained following skimming by title to select full-text publications for eligibility according to the inclusion/exclusion criteria.The reference list of each article was screened in order to find additional original articles.

Data Extraction
Two authors (A.B and J.B.) conducted the data extraction independently.A third author (J.H.V.) resolved discrepancies.Reviewers were not blinded to information regarding the authors, the journal, or the outcomes for each article reviewed.A standardized form was used to extract data concerning study design, number and mean age of participants, year and country of publication, setting, expectation association with outcome, clinical outcome measures, and reported findings.The form was developed according to the directions of the Cochrane Handbook for Systematic Reviews of Interventions.

Quality assessment
RCTs' methodological quality was evaluated using the PEDro scale.The PEDro scale is an 11-item scale designed for rating the methodological quality of RCTs.Each item that is satisfied on the scale contributes one point to the total possible score of 10 points.
The Methodological index for non-randomized studies (MINORS) has been used to assess methodological quality and risk of bias.The tool is comprised of 16 and 24 items for non-randomized studies and comparative studies, respectively, and each item is scored from 0 to 2 (Slim et al., 2003).

Data analysis plan
We planned to perform a systematic review by descriptively presenting the results of the retrieved studies.

Selection of studies
Originally 506 papers were identified through the database search.Once duplicates were removed and the titles and abstracts of all remaining unique articles were analyzed, 12 full-text articles were analyzed to verify their eligibility for inclusion in the present study.Five of these articles were excluded.Seven studies were finally selected for this review and 1 study was included from secondary research (Gribble & Robinson, 2009;Kosik et al., 2020;McCann et al., 2018;McCann et al., 2017;Mulligan & DeVahl, 2020;Negahban et al., 2013).The flow of studies through the review process can be found in Figure 1.

Quality assessment
The NIH quality assessment tool for observational cohort and cross-sectional studies was used to assess the quality of the article realized by Kosik et al. in 2020 e by Webster et al. in 2016(Kosik et al., 2020;Webster et al., 2016), that result respectively "fair" and "poor".The results of the NIH quality assessment tool can be found in Table 1.
The MINORS scale was used to assess the quality of the study realized by Mulligan et al in 2020 and the study realized by Fatima et al. in 2016, and results of the analysis was respectively 18/24 and 19/24.The results of the MINORS scale can be found in Table 1.The risk of bias analysis of the study realized by Mulligan et al. in 2020(Mulligan & DeVahl, 2020) (Gribble & Robinson, 2009;McCann et al., 2018;McCann et al., 2017;Negahban et al., 2013).The results of the CASP tool can be found in Table 1 and Table 2.The results of this study showed that, regardless of age, participants with CAI had decreased isometric hip extension compared to the control group, but not LAS group.There were no differences between groups in isometric knee extension strength and isometric hip abduction strength.
The results from the current study provide evidence that highlight the need for clinicians to assess potential strength throughout the lower extremity when identifying specific impairments in patients with CAI.Gender->16 F, 14 M Knee flexion and extension and hip flexion and extension were investigated.A few practice trials were performed, and then the subjects performed five continuous maximal effort trials.After the procedures for the first designated test joint were completed for both limbs, a 10-minute rest period was provided, then the procedures were repeated for the second designated joint.
The results of this study showed that there were statistically significant differences for average peak torque during knee flexion and extension.There were no statistically significant relationship during hip movements. The

Data from studies
Below are reported the results of the eigth studies included in this review.
1.The aim of the study realized by Gribble et al in 2009 (Gribble & Robinson, 2009), was to determine whether chronic ankle instability (CAI) is associated with deficits in the ankle, knee, and hip torque.The subjects with CAI demonstrated significantly less average peak torque (APT) production for knee flexion (F1,28 = 5.40; p = 0.03) and extension (F1,28 = 5.34; p = 0.03).Subjects with CAI showed significantly less APT for ankle plantar flexion in the injured limb compared with their noninjured limb (F1,28 = 6.51; p = 0.02).No significant difference in ankle dorsiflexion or hip flexion/extension APT production existed between the 2 groups.Individuals with CAI, in addition to deficits in ankle plantar flexion torque, had deficits in knee flexor and extensor torque, suggesting that distal joint instability may lead to knee joint neuromuscular adaptations.There were no similar deficits at the hip.
2. The purpose of the study realized by Kosik et al in 2020 (Kosik et al., 2020), was to compare ankle, knee, and hip isometric peak torque between people with CAI, copers, and un-injured controls.The results indicated a significant interaction between age and injury specifically in dorsiflexion.It was observed that middle-aged un-injured controls (p<0.001) and copers (p<0.001)exhibited lower isometric peak torque compared to their young adult counterparts.However, no differences were found between young and middle-aged adults with CAI (p>0.05).The results indicated a significant interaction between age and injury specifically in dorsiflexion.It was observed that middle-aged un-injured controls (p<0.001) and copers (p<0.001)exhibited lower isometric peak torque compared to their young adult counterparts.However, no differences were found between young and middle-aged adults with CAI (p>0.05).In conclusion, results showed that regardless of age, isometric ankle and hip peak torque was lower in participants with CAI compared to un-injured controls, but not copers.
3. The article realized by McCann et al in 2017 (McCann et al., 2017), was a single-blinded, crosssectional, case-control study.The objective of this paper was to examine isometric hip strength in those with and without CAI and determine the degree of Star Excursion Balance Test (SEBT) variance explained by isometric hip strength.The CAI group had lower SEBT-ANT scores compared to LAS copers (P=0.03) and controls (P=0.03).The CAI group had lower ABD compared to LAS copers (P=0.03) and controls (P=0.02).The CAI group had lower ER compared to LAS copers (P=0.01) and controls (P=0.01).ER (R2=0.25,P=0.01) and ABD (R2=0.25,P=0.01) explained 25% of the CAI group's SEBT-PM and SEBT-PL variances, respectively.In conclusion, the CAI group had deficient dynamic postural control and isometric hip strength compared to LAS copers and controls.Additionally, the CAI group's isometric hip strength significantly influenced dynamic postural control performance.
5. The aim of the study realized by Mulligan et al in 2020 (Mulligan & DeVahl, 2020), was to determine if deficits in weight-bearing and non-weight-bearing assessment of hip strength or dynamic balance in lower extremity reaching tasks from flat and inclined surfaces can differentiate subjects classified as controls, ankle sprain copers, or those with chronic, recurrent ankle sprains.There were no significant differences between groups in self-report of Foot and Ankle Ability Measures or Tegner activity levels.Mean hip strength was not significantly different between ankle sprain classification groups (p = 0.66 -0.82).The mean limb symmetry index for hip strength comparing injured and uninjured ankles was nearly symmetrical in all ankle stability groups (p = 0.34 -0.97).The same symmetry was present when comparing injured and uninjured abilities for all dynamic balance reach tasks from both flat and inclined surfaces.(p = 0.16 -0.62).There was a fair relationship between hip extension and weight-bearing hip extension/external rotation strength and the posteromedial and posterolateral reach tasks with correlation coefficients in the range of 0.33 -0.43.In conclusion, performance measures of tri-planar, static, isometric hip strength, and lower extremity reach in dynamic balance tasks could not differentiate subjects without a history of injury from those subjects with one or more lateral ligamentous ankle sprains.
6.The purpose of the case-control study realized by Negahban et al in 2013 (Negahban et al., 2013) was to investigate the eccentric torque production capacity of the ankle, knee, and hip muscle groups in patients with unilateral chronic ankle instability (CAI) as compared to healthy matched controls.Results showed that there was no significant interaction of group (CAI and healthy controls) by limb (injured and non-injured) for any muscle groups.The main effect of the limb was not significant.The main effect of the group was only significant for an eccentric torque production capacity of ankle dorsi flexor and hip flexor muscle groups.The APT/BW ratio of these muscles was significantly lower in the CAI group than in the healthy controls (P<0.05).In conclusion, CAI is associated with eccentric strength deficit of ankle dorsi flexor and hip flexor muscles as indicated by a reduction in torque production capacity of these muscles compared to healthy controls.This strength deficit appeared to exist in both the injured and non-injured limbs of the patients.
7. The objective of the clinical controlled trial realized by Fatima et al.(Fatima, Bhati, Singla, Choudhary, & Hussain, 2020) was to investigate the EMG activity via maximum voluntary isometric contraction (MVIC) of the hip muscles (Gmed and Gmax muscle) during different functional exercises (Y balance and single-leg squat with and without swiss ball) in CAI subjects vs age-matched healthy controls.Results showed that EMG activity of the Gmed and Gmax muscles was significantly different between CAI (lower percent MVIC) and healthy controls but it did not differ significantly across the functional exercises (significant main effect of group F [1.32] = Gmax 86.24/ Gmed 40.40 --> P <.001; insignificant main effect for task F [2.335, 32] = 0.181 --> P = .866).In conclusion, although EMG activation patterns of hip musculature (Gmed and Gmax) are significantly different between subjects with CAI and healthy controls, both tested muscles activity do not vary during functional task within each group.
8. The aim of the study realized by Webster et al. (Webster, Pietrosimone, & Gribble, 2016) was to examine the prefatigued and postfatigue EMG activity of Tibialis anterior (TA), Peroneus longus (PL), Gmed and Gmax in individuals with or without CAI before and during the landing of a lateral hop.The authors introduced a fatigue protocol consisted of 5 X 5-m cone drills involving combination of forward sprints, lateral shuffles, pivoting, and backward running.Next, participants completed 30 2footed lateral hops over a 10-cm barrier, followed by 3 successive step-ups onto and 2-footed hop-downs from boxes measuring 30, 38, and 46 cm high.The participants had to repeat the protocol until fatigue, defined as (1) 50% increase in their fastest time to complete the course, (2) inability to repeatedly clear the 10-cm barrier on the lateral jumps, (3) inability to step onto the plyometric box, or (4) unwillingness to continue.The results showed that the activation higher of the PL and Gmax was higher in the CAI than in the control group during the prelanding phase of a lateral hop.After introduction of functional fatigue, the authors observed differences with moderate to strong effect sizes in the postfatigue results for the PL and Gmax, demonstrating clinical importance.

Discussion
The purpose of this study was to determine the correlation between people that suffer from chronic ankle instability and muscle strength deficits in the proximal joints of the lower limb.
Consistent with the different types of intervention investigated, strength was considered as an outcome measure selected by the studies included in this systematic review.In particular, force production of the hip and knee was analyzed in participants with CAI.Four of the studies (McCann et al., 2018;McCann et al., 2017;Mulligan & DeVahl, 2020) analyzed included lateral ankle sprain (LAS) coper group and uninjured controls, while the four others studies (Fatima et al., 2020;Gribble & Robinson, 2009;Negahban et al., 2013;Webster et al., 2016) included an uninjured control group only.Early studies considered frontal plane ankle strength mainly relates to CAI (Lentell et al., 1995;Wilkerson, Pinerola, & Caturano, 1997;Willems, Witvrouw, Verstuyft, Vaes, & De Clercq, 2002), but inconsistent findings led to the interpretation that inversion and eversion muscles are not highly correlated with CAI (Kaminski & Hartsell, 2002).For this reason, more recent research focused their finding to investigate a possible correlation between CAI and sagittal muscle strength deficits.
Muscle strength continues to decline with age and is a prominent contributor to physical performance later in life (Tieland, Trouwborst, & Clark, 2018;Enríquez Reyna, et al., 2019) that can significantly impact a person's healthrelated quality of life (Houston, Hoch, & Hoch, 2015) and the ability to remain physically active (Houston et al., 2015;Villafane et al., 2016).Despite this, divergent results are identified.Regardless of age, it appears that participants with CAI had decreased sagittal plane strength, in particular isometric hip extension, compared to the control group, but not the LAS group when included.In support of that, Hubbard et al. (Hubbard, Kramer, Denegar, & Hertel, 2007) found differences in isometric hip extension and abduction strength between the involved side of the CAI group compared to the involved side of the control group.However, these results seem to be in contrast with 60% of the studies included in this review.Not strictly differences between CAI group, LAS coper, and control group were identified during hip extension.
Another research (Friel, McLean, Myers, & Caceres, 2006) observed hip abductor muscle strength and plantar flexion were significantly less on the involved side than on the uninvolved side (P < .001 in each case).The strength of the involved hip abductor and hip extensor muscles was also significantly correlated (r = 0.539, P < 0.01).In this specific case, it's important to consider that the uninvolved limb had served as the control because uninjured controls were not involved.However, the studies analyzed in this review disagree in supporting the correlation between hip abduction strength deficit and CAI.
To our knowledge, a low side of previous studies investigated knee muscle strength in individuals with CAI, LAS coper, and uninjured controls.Gribble and Robinson (Gribble & Robinson, 2009) identified statistically significant differences in knee flexion and extension which were not observed in the most recent article identified by research (Kosik et al., 2020).Interestingly, comparing these two papers no statistically significant relationship during hip movements were observed (Gribble & Robinson, 2009).The different methodologies used between these two studies, particularly isometric (Gribble & Robinson, 2009) vs. concentric (Kosik et al., 2020) contraction, might explain the varying results.
An interesting result betrays that a significant difference between CAI and controls has been observed only for eccentric torque production of the hip flexor muscle group.This specific result, unfortunately, was not investigated or formerly declared in precedent research.

Limits
The main limitation that we noticed in this review is represented by a number of included studies that was relatively small.Also, the different selection criteria, scales and questionnaire adopted, and the numerousness of the population strictly limit the ability to generalize potential evidence to the target patients.Finally, despite our effort to search for three databases, some articles may not have been intercepted by our search string, determining possible selection bias.However, we have ensured the quality standard in reporting this systemic revision by adopting the PRISMA guidelines.

Conclusion
Correlations between chronic ankle instability and muscle strength deficits of the proximal joints of the lower limb seem to be noticed in clinical practice, regardless of age, in most of the studies included.However, the authors did not concur on which joints and muscles group were involved.For this reason, it's not possible to confirm to our knowledge a strictly significant correlation between strength deficit of hip and knee, when appreciated.These results, however, might suggest another time that the difference between people who suffer from CAI and coper is the rehabilitation program that patients follow after an injury.In this perspective, clinicians might focus their attention on the impairments identified and include strength conditioning when needed.
was realized using the risk-of-bias tool for non-randomized trials (ROBINS-I).Results from ROBINS-I are reported in Table n.4.The CASP tool was used to assess the quality of the four case-control included in the review: McCann et al 2017, McCann et al 2018, Negahban et al 2013, Gribble et al. 2009

Figure 1 .
Figure 1.Flow diagram of studies throught the different phases of the review