The Biomechanical and Functional Status of Patients with Knee Osteoarthritis - A Cross Sectional Study

Introduction

Knee osteoarthritis (KOA) is a musculoskeletal condition involving degeneration of knee cartilage, resulting in pain and functional limitations. Patients with knee OA show decreased range of motion (ROM) and increased ground response force. In fact, we frequently see knee osteoarthritis patients with pathology in the hip and ankle joints. The knee deformity known as genu varum (GV) occurs when the mechanical axis of the lower limb crosses the middle of the knee joint. The deformity typically results from uneven pressure being applied to the medial and distal compartments of the knee, which eventually damages cartilage within the joint. Genu valgum is a deformity that causes a person’s knees to curve inward and touch one another, giving them a “knock-knee” appearance. The proximal tibia’s medial torsion, which increases the weight bearing capacity of the lateral side, is the most frequent cause of genu valgum [1].

Cadence is a common and simple indicator of physical activity (PA) during free-living behaviour. A cadence of 100 steps/min is moderate intensity and a cadence of 130 steps/ min is vigorous intensity. Knee varus and valgus are effective on the hindfoot alignment and disrupts the coronal hip- knee-ankle alignment. Hindfoot angle is the angle between the tibial anatomical axis and the longitudinal axis of the calcaneus. The normal hindfoot angle is 2° to 6° valgus [2]. The angle was formed by the bisection of the distal one-third of the leg and a longitudinal line that bisected the posterior aspect of the calcaneus. A hindfoot angle of more than 7° was defined as excessive valgus heel alignment.

Hip joint movements like internal rotation should also change as OA in the knee with varus or valgus malalignment develops. Hip internal rotation ranges from 0-40° in gonimoteric measurements. Knee flexion is a major osteokinematic motion which ranges normally from 0-140°. In individuals affected with osteoarthritis knee usually there will be a decrease in knee flexion.

Western ontario and mcmaster universities osteoarthritis index (WOMAC) is a scale used to evaluate the disease’s course or a patient’s reaction to treatment in those with knee or hip osteoarthritis. There are three subscales: 1) pain severity during various positions or movements, 2) severity of joint stiffness, and 3) difficulty performing daily functional activities. The total score is of 96 in which each subscale is the sum of scores for each response to each item. Possible subscale scoring in the Likert format is: pain (0- 20; 5 items each scored 0-4), stiffness (2 items, 0-8), and physical function (17 items, 0-68). The VAS pain rating scale is dependable, valid which consists of a bidirectional 10 cm straight line with two labels at either end, reading “no pain” and “worst possible pain.” The scale runs from 0 to 10, with 0 denoting “no pain” and 10 denoting the “worst pain imaginable.” Patients are told to select the one number on the scale that most accurately describes their level of pain [3].

This study is conducted to analyze these parameters like cadence, hindfoot angle, hip internal flexion, knee flexion, WOMAC scale and VAS pain rating scale between the groups of individuals with genu valgum and genu varum deformity. Previously there have been numerous studies on genu valgum and genu varum separately but an analysis between these deformities has not been conducted till date. There are many studies involving several outcome measures with OA knee but there has always been a lack in studies on genu valgum and varum deformity caused by OA knee. Analyzing these two deformities using various parameters will be helpful in creating a wide knowledge while treating a patient with knee osteoarthritis. Therefore, this study is will help to know about the biomechanical and functional status of OA knee patients with genu valgum and varum deformity [4].

Methodology

Study Setting: Community setting Study Design: Cross sectional study Sample Size: 80 Sampling Method: Convenient sampling Study Duration: 6 months

Procedure

After ethical approval, Data were taken from the ward members and ASHA workers in Kochi taluk area (community level). Only subjects who were clinically diagnosed with knee osteoarthritis were included. The subjects were selected according to the inclusion and exclusion criteria. The nature of study, the duration of intervention and the intervention being used will be briefed to the participants. They will be encouraged to clarify queries regarding the study, if any.

A total of 80 knee OA patients were conveniently divided into two groups; one with genu valgum and other with genu varum by assessing the medial tibiofemoral angle. Operational tool used for medial tibiofemoral angle is 360° goniometer. Normal range of medial tibiofemoral angle is 180°-185°. If the angle is below 180° the patients is with genu varum deformity. If medial Tibiofemoral angle is above 185° then it is considered genu valgum deformity. Mid-point of patella is used as fulcrum. Both ASIS and mid-point of ankle is taken respectively as stationary arm and movable arm point. After classifying the patients into two groups, the following parameters were checked which are cadence in gait, decreased knee flexion, hip internal rotation, hind foot angle, WOMAC scale, VAS pain scale. The deviations in the parameters were compared between the genu valgum group and genu varum group. The data were properly studied and the conclusion was prepared accordingly.

Discussion

This study was conducted to know about the biomechanical and functional status of OA knee patients with genu valgum and genu varum deformity. In this study, patients with knee osteoarthritis were divided into two groups which are genu valgum and genu varum group by using tibiofemoral angle. Outcomes measures used in this study were cadence, WOMAC scale, VAS pain scale, hip internal rotation ROM, knee flexion ROM and hindfoot angle [5].

These were checked in each group and a comparison was taken between them. The results were analysed using t test. Independent t test was used to compare results between the groups. Significant level kept as p value ≤ 0.05.

In case of cadence, it was found that in independent t test, since t value is 3.55, shows p value ≤ 0.05(0.0006), The mean difference shows the difference between mean in two groups is 5.11. The statistical analysis of cadence shows genu valgum group has more significant increase when compared to genu varum group. Jocelyn FH, et al. [6] stated that cadence is effectively lower in osteoarthritis knee patients compared to normal individuals. In this study, cadence was seen to be higher in genu valgum group compared to genu varum group. We observed that genu varum group have higher base of support as a result their gait pattern is slower. Waddling gait was seen in patients with genu varum deformity. As a result, their cadence was much lower compared to genu valgum group.

In case of hip internal rotation ROM, it was found that in independent t test, since t value is 2.37, shows p value ≤ 0.05(0.01), The mean difference shows the difference between mean in two groups is 2.386. The statistical analysis of hip internal rotation ROM shows genu valgum group have more significant increase when compared to genu varum group. Ro DH, et al. [7] stated that hip ROM was reduced in knee osteoarthritis patients compared to the control group with normal individuals. Genu valgum deformity are already seen in mild internal rotation of hip compared to genu varum. Genu varum group have outward bending of knee which results in decreased hip internal rotation. As a result, there is significant difference in hip internal rotation ROM for genu varum and genu valgum groups.

In case of knee flexion ROM, it was found that in independent t test, since t value is 3.09, shows p value ≤ 0.05(0.002), The mean difference shows the difference between mean in two groups is 5.521. The statistical analysis of knee flexion ROM shows genu valgum group has more significance when compared to genu varum group. Janie LA, et al. [8] found out changes in peak knee flexion moment in both moderate and severe knee osteoarthritis patients. Genu varum group had decreased knee flexion ROM compared to genu valgum group. Fixed flexion deformity is commonly seen in genu varum deformity rather than in genu valgum. As a result, there will be tightness over the hamstrings muscles which will lead to reduction in knee flexion motion.

In case of Hindfoot angle, it was found that in independent t test, since t value is -1.99, shows p value ≤ 0.05(0.049), there is significant difference in hindfoot angle value between the genu valgum and genu varum groups. The mean difference shows the difference between mean in two groups is 0.427. The statistical analysis of hindfoot angle shows genu varum group has more significant change compared to genu valgum group. Ruhling M, et al. [9] stated that a varus deformity at the knee joint can lead to a hindfoot valgus and consequently to a pes planus deformity, for instance. In this study, genu varum patients were higher in number compared to genu valgum group. As a result, most of the individuals were having hindfoot valgus which normally leads to flat foot deformity (pes planus).

In case of the WOMAC scale, it was found that in independent t test, since t value -1.38, shows p value ≥ 0.05(0.169), there is no significant difference in WOMAC scale value between the genu valgum and genu varum groups. The mean difference shows the difference between mean in two groups is 2.823. The statistical analysis of WOMAC scale shows either genu valgum group or genu varum group has no significance compared with each other.

In case of VAS pain scale, It was found that in independent t test, since t value 0.064, shows p value ≥ 0.05(0.948), there is no significant difference in VAS pain rating scale value between the genu valgum and genu varum groups. The mean difference shows the difference between mean in two groups is 0.021. The statistical analysis of VAS pain rating scale shows either genu valgum group or genu varum group has no significant change compared with each other [10, 11, 12].

Conclusion

Based on the values of the above study, the scores in the genu valgum group shows statistically significant increase in cadence, hip internal rotation ROM and knee flexion ROM compared to genu varum group. Only in the case of hindfoot angle, there is a significant increase for genu varum group over genu valgum group. The values of both the WOMAC scale and VAS pain rating scale remained largely unchanged since the scores were comparable in both groups. This study also suggests that in knee OA pateints, genu varum group are having more functional and biomechanical limitations compared to genu valgum group. As a result, this study’s conclusion suggests that when examining specific outcome measures such as cadence, hip internal rotation range of motion (ROM), knee flexion ROM, and hind foot angle between the genu valgum and genu varum groups, significant differences are observed. However, the WOMAC scale and VAS pain rating scale are more valuable in determining the quality of life and the severity of pain rather than comparing changes.