Foot posture assessment in people with primary medial compartment knee osteoarthritis: An observational study :Prajakta Milind Gosavi, Sona S Kolke, Jay Chitre, Ashok Shyam, Parag Sancheti, Physiotherapy - The Journal of Indian Association of Physiotherapists

ORIGINAL ARTICLE
Year : 2021 | Volume : 15 | Issue : 1 | Page : 12--16

Foot posture assessment in people with primary medial compartment knee osteoarthritis: An observational study

Prajakta Milind Gosavi¹, Sona S Kolke², Jay Chitre¹, Ashok Shyam³, Parag Sancheti³,
¹ Sancheti Institute College of Physiotherapy, Pune, Maharashtra, India
² Department of Musculoskeletal Physiotherapy, Sancheti Institute College of Physiotherapy, Pune, Maharashtra, India
³ Sancheti Institute of Orthopedics and Rehabilitation, Pune, Maharashtra, India

Correspondence Address:
Dr. Sona S Kolke
11/12, Sancheti Healthcare Academy, Thube Park, Shivaji Nagar, Pune - 411 005, Maharashtra
India

Abstract

BACKGROUND: Foot postures are integral to the biomechanical alignment and the dynamic function of the lower extremity. This study compared foot postures in people with primary medial compartment osteoarthritis (OA) and age-, gender-, and body mass index (BMI)-matched controls using various foot measures. Grade-wise variations were also assessed. AIM: The aim of the study was to assess the foot postures in people with primary medial compartment knee OA. METHODS: This was an observational, analytical study and the subjects were recruited by convenient sampling from tertiary hospitals in Pune. The target population were primary knee OA who were clinically and radiologically diagnosed for their severity based on the Kellgren–Lawrence grading, a severity classification based on radiographic evidence. The Centre of Rheumatic Diseases version of Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and the Foot Function Index (FFI) which are both self-report questionnaires were duly filled by the knee OA subjects for the pain and dysfunction of the knee and foot, respectively. The control group consisted of age-, gender-, and BMI-matched asymptomatic healthy subjects. Foot postures of all subjects namely, the OA (n=48) and controls (n = 33) were assessed using the foot posture index (FPI), arch index, and navicular drop test. The FPI as well as the navicular drop test categorized the subjects into 3 groups: pronated, neutral, and supinated. The arch index was calculated from the inked imprint of the foot of the affected limb where higher values indicated dropped arch. STATISTICAL ANALYSIS AND RESULTS: Independent samples Mann–Whitney U-test and unpaired t-test were used to investigate the differences between the two groups in the foot characteristics. The Spearman's rho was used to analyze the correlation of FPI with the grades of OA and of WOMAC with the FFI within the OA group. The study included 48 medial knee OA subjects (48 knees and the corresponding foot) and 33 age-, gender-, and BMI-matched healthy controls. The percentages of foot postures (neutral, pronated and highly pronated) of both groups were 71%, 25% and 4% respectively in the OA group and 92%, 2% and 6% respectively in the control group. Comparative study of foot postures between the two groups showed more pronated feet in the OA group (P < 0.001). Correlation of the FPI scores with the grades of OA showed no association (β = −0.005; P = 0.97) and between WOMAC and the FFI in the knee OA group showed weak association. (β = 0.0349; P < 0.05). CONCLUSION: The foot postures were altered in the knee OA group as compared to healthy controls, with the OA group showing more pronated foot type.

How to cite this article:
Gosavi PM, Kolke SS, Chitre J, Shyam A, Sancheti P. Foot posture assessment in people with primary medial compartment knee osteoarthritis: An observational study.Physiother - J Indian Assoc Physiother 2021;15:12-16

How to cite this URL:
Gosavi PM, Kolke SS, Chitre J, Shyam A, Sancheti P. Foot posture assessment in people with primary medial compartment knee osteoarthritis: An observational study. Physiother - J Indian Assoc Physiother [serial online] 2021 [cited 2023 Mar 21 ];15:12-16
Available from: https://www.pjiap.org/text.asp?2021/15/1/12/324124

Full Text

Introduction

Osteoarthritis (OA) is primarily a degenerative condition characterized by destruction of articular cartilage, with the knee being the most commonly affected joint with an approximately 45% lifetime risk of developing symptomatic OA in at least one knee.[1],[2] In India, the overall prevalence of knee OA was 28.7%.[3] A normal knee joint has the ground reaction forces (GRF) passing medial to the central axis of the joint, leading to 60% more weight bearing on the medial compartment, making it more prone to degenerative changes. With the wear and tear of cartilage due to OA, the narrowing of the medial joint space, leading to a varus malalignment of the knee which takes the GRF further away from the central axis of the joint, leading to an increase in the compressive forces in the medial compartment to approximately 70%–80%.[4] Patients, thus, adopt compensatory strategies such as lateral trunk lean to the same side along with alterations in the ankle and subtalar joint. A pronation movement at the subtalar joint and a toe-out gait pattern helps shifting the center of pressure laterally to move the GRF closer to the knee joint, thereby reducing the knee loads. The degree of genu varum that can be compensated by pronation at the foot, however, depends on the available range of motion at the ankle, subtalar joint, and the midtarsal joints.[5],[6],[7]

Investigation into the walking pattern in young adults by Bart Van Gheluwe et al. had the healthy participants simulating the scissors gait, genu varum gait, and the genu valgum gait and observed that simulated genu varum walking led to a pronation moment at the subtalar joint.[8] Levinger et al. observed that primary medial knee OA exhibited more pronated foot type compared with matched healthy controls.[9] Comparable results were observed by Ohi et al. who found an association between the frontal plane knee alignment, hallux valgus and calcaneal angle in patients with medial knee OA.[10] Reilly et al. analyzed the foot postures of three groups consisting of hip OA, medial knee OA, and healthy age-matched controls and found significant differences in the foot posture index (FPI) scores: the hip OA group had supinated feet, the medial knee OA group had pronated feet, and the healthy controls had a median FPI scores which were closer to the neutral feet. However, they could not conclude whether the foot influences were the cause or a consequence of the disease process.[11]

Foot posture being an important contributor to the lower limb kinetic chain, its alterations in the disease process of knee OA need to be assessed. The possible interaction of the foot posture with the radiological evidence of severity of knee OA has limited evidence. Thus, the primary objective of the study was to assess the foot posture and its alterations in the primary knee OA subjects as compared with healthy controls. The study secondarily aims to observe if the foot postures vary according to the grades of OA.

Methods

Ethical statement

The study was approved by the Institutional Ethical Committee and was conducted in accordance with the Helsinki Declaration. All subjects were informed about the procedure and prior consent was taken for their participation in the study.

Recruitment

This was an observational, analytical study and the subjects were recruited by convenient sampling from tertiary hospitals in Pune. The target population were primary knee OA who were clinically and radiologically diagnosed for their severity based on the Kellgren–Lawrence (K/L) grading, a severity classification based on radiographic evidence. The knees are categorized into four grades, with mild OA having K/L Grades 1–2 and severe OA with KL Grades 3–4. The subjects with K/L Grade 1 were excluded as they are subclinical/asymptomatic and have absence of malalignment in the knee joint. Thus, the inclusion criteria included subjects with K/L Grades 2–4 who were able to walk independently (with or without an assistive device). The OA group included subjects with unilateral or bilateral knee; in bilateral affection, the most affected knee was considered as the index knee.[12] Subjects were excluded if they had a history of any recent trauma or surgical procedure to the lower extremities in the past 12 months, congenital deformity, or previously diagnosed foot conditions. The control group consisted of 33 age-, gender-, and body mass index (BMI)-matched asymptomatic subjects who were recruited from various housing societies across Pune.

Procedure

The demographic data of the subjects such as age, gender, weight (kg), height (m), and BMI were noted. The most symptomatic knee in the OA group and the corresponding knee in the control group were assessed. All subjects with OA filled up the self-administered questionnaire of the Centre of Rheumatic Diseases (CRD) version of the Western Ontario and McMaster University Arthritis questionnaire (WOMAC) and the Foot Function Index (FFI), both of which are validated tools used to measure pain and dysfunction in the knee and foot, respectively.

The CRD version of WOMAC questionnaire (CRD [Pune] version which is also available in local languages of Marathi and Hindi) is a modified and validated version of the original WOMAC which consisted of 27 questions based on pain, stiffness, and difficulty. The CRD version has three additional questions (original WOMAC having 24 questions) based on functional limitations faced by the patients due to knee OA in the Indian scenario. The questions are scored on a scale of 0–4, which correspond to: none (0), mild (1), moderate (2), severe (3), and extreme (4). Higher scores correspond with worse pain, stiffness, and functional limitations.[13]

The FFI questionnaire consisted of 23 self-report items based on the pain, disability, and activity limitations in the foot faced by the patients.[14] The FFI had the subjects scoring each question with a visual analog scale which ranged from 0 (no pain or difficulty) to 10 (worst pain imaginable or so difficult it requires help). Higher scores corresponded to worse pain and function.

The assessment of the foot posture included (1) FPI, (2) arch index, and (3) navicular drop test. All the measurements were done by a clinical therapist with more than 10 years of clinical experience. (1) The FPI is a six-component foot posture assessment method designed by Redmond et al., which needs the subject to stand in a relaxed bipedal weight-bearing position. The six components of the FPI included (a) talar head palpation, (b) curves above and below the lateral malleoli, (c) calcaneal angle, (d) talonavicular bulge, (e) medial longitudinal arch, and (f) forefoot to rearfoot alignment. Each component was scored on a 5-point scale from −2 to +2. It is scored as a total ranging from −12 (highly supinated) to +12 (highly pronated). Raw FPI scores were converted to Rasch scores to use it as interval data for statistical analysis.[15],[16],[17] (2) The arch index was measured with the subject standing on a graph paper in a relaxed weight-bearing position with ink applied to the sole of the foot. The static foot print obtained was divided equally into three parts. Arch index was then calculated as the ratio of area of the middle section to the area of the entire footprint.[18] Higher values of the arch index indicated a flat arch. (3) Navicular drop measurements were taken with the subjects in subtalar joint neutral position (STNJ) and in a relaxed standing position. STNJ position was defined as the position of foot where the talar head could be palpated anterior to the ankle mortise, equally prominent medially and laterally. Vertical height of the naviculum was noted in STNJ position and then the participant standing in relaxed bipedal stance. Navicular drop was the difference between the two heights. The measurements indicated supinated (<5 mm), neutral (6–8 mm), and pronated (>10–15 mm).[19],[20]

Statistical analysis

All analyses were performed using IBM Corp. Released 2019. IBM SPSS Statistics for Windows, Version 26.0. Armonk, NY: IBM Corp. Descriptive statistics were used for analysis of demographic data. Raw FPI scores were converted to Rasch Scores to use it as interval data. Differences between the two groups were assessed using independent samples for continuously scored variables and the Shapiro–Wilk test was used to analyze the normality distribution of the data. The FPI and Navicular drop scores were significant, indicating that they were not distributed normally; hence, the nonparametric Mann–Whitney U-test was used to compare differences between the two groups. The arch index was nonparametric data and was analyzed with Mann–Whitney U-test between the two groups. The Spearman's rho test was used to analyze the correlation (within the OA group) of the FPI scores with grades of OA and of the WOMAC with FFI scores.

Results

A total of sixty subjects with primary knee OA were screened for their severity of KL grades. Eight subjects of K/L Grade 1 were excluded whereas four subjects refused consent. Thus, forty eight subjects (unilateral or bilateral OA) with 48 knees (the most affected knee as the index knee in bilateral affection) and their corresponding foot were considered for analyses. The control group consisted of thirty-three age-, gender-, and BMI-matched asymptomatic subjects whose corresponding knee and foot were considered for analysis.

Both groups were age, gender, and BMI matched and their demographic characteristics are in [Table 1].{Table 1}

Comparison of the foot postures showed the OA group having significantly more pronated foot type compared to the healthy controls. Significant differences were found between two groups in relation to the mean scores of the FPI and navicular drop test. No significant difference was found for arch index [Table 2].{Table 2}

No significant grade-wise variations were seen in the foot postures (FPI) (β = −0.005; P = 0.97). The mean WOMAC scores and FFI scores of the OA group were 45.19 ± 19.09 and 3.33 ± 9.53, respectively. The study found a weak correlation between the functional outcome scores of the knee and foot, i.e., WOMAC scores and FFI scores, respectively (β =0.0349; P < 0.05) [Table 3].{Table 3}

Discussion

In this study, the foot postures of subjects with primary medial knee OA were analyzed and compared with matched healthy controls using three foot assessment measures, viz., the FPI, Navicular drop test, and medial arch index. The results showed subjects with medial compartment knee OA having more pronated foot type as compared to the controls [Table 2], which was indicated by two measures: FPI and the navicular drop showing medium-to-large effect sizes. We, however, did not find the arch index to be a sensitive indicator of differences between the two groups. We found weak correlations between the functional outcomes of the knee and foot, i.e., the WOMAC and FFI scores. There was no association between FPI and the grades of OA. This could be explained by the fact that we had fewer subjects belonging to the severe knee OA (KL Grade 3 and 4) and 31/48 subjects (64.5%) belonging to KL Grade 2.

The results were comparable with Levinger et al., where 32 knee OA subjects were compared with 28 age- and gender-matched controls using similar foot measures of FPI, the navicular drop, and arch index, although they also found significant differences in the arch index. A further investigation done by Levinger et al. in 2012 analyzed for motion of the tibia, rearfoot, and forefoot and showed people with medial compartment knee OA having less mobile, more everted rearfoot with internal rotation of the tibia throughout the gait cycle.[9],[21] A Framingham Foot and OA study done in 2012 on 1903 participants by Gross et al. adapted the Staheli Arch Index to quantify standing foot morphology from pedobarographic recordings. They observed that the most planus feet had 1.3 times (95% confidence interval) the odds of knee pain and 1.4 times the odds of medial tibiofemoral cartilage damage.[22] Abourazzouk et al. in a similar study done in Morocco used the FPI, the navicular drop showed pronated foot posture and flat foot to be significantly associated with medial compartment knee OA.[23] However, a study done by Al-Bayati et al. found results on the contrary. They measured the medial joint space width (mJSW), condylar angle, anatomic axis angle, tibial plateau angle, and condylar plateau angle on the digital anteroposterior knee radiographs. The WOMAC questionnaire was used to assess pain and the functional status of the patients, while foot posture was assessed using FPI. They observed that the higher grades of OA had more supinated feet with higher WOMAC scores, while the varus alignment at knee correlated with foot pronation. The observations were contradictory as higher grades of OA with reduced mJSW are associated with genu varum.[24] Ohi et al. in a cross-sectional study recruited 102 medial knee OA subjects with different severity and studied the frontal plane knee alignment and foot postures in analyzing the anatomic axis angle of the tibiofemoral and three-dimensional foot scanning automated machine. They observed the varus alignment of the knee led to a rear foot pronation as a compensatory mechanism to keep the foot plantigrade. However, contrary to the above hypothesis found increased varus alignment in severe OA to be associated with supinated feet.[10]

The limitations of the current study were that the majority of the OA subjects were KL Grade 2 (64.5%). We had very few subjects of the more severe K/L Grade 3 and 4 to analyze the effect of genu varum on the foot posture. Furthermore, the level of activity of the subjects which has a direct impact on foot posture was not assessed. Studies in future could consider better representation of the all grades of OA with larger samples to analyze the association between the frontal plane alignment and severity of knee OA with the foot postures and function. Although there were significant differences in the foot postures in subjects with knee OA as compared to asymptomatic healthy controls, it could not be determined through the study whether foot alterations were due to the disease process or preceding it.

Conclusion

People with medial compartment knee OA exhibited a more pronated foot type as compared to the control group.

Acknowledgments

We would like to thank Dr. Rachana Dabadghav (PT) for guiding us through the statistical analysis. We would like to acknowledge Dr. Arvind Chopra for his kind permission to use their CRD (Centre of Rheumatic Diseases) version of the WOMAC Questionnaire. We would like to thank the committee of Athashree society, Baner, Pune, for granting us the permission for collecting the data. We would like to thank the various yoga clubs in the city who granted us permission for data collection.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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