Pelvis/lower extremity alignment and range of motion in knee osteoarthritis: A case-control study in elderly Japanese women

Abstract

BACKGROUND:

The prevalence of radiographic knee osteoarthritis (OA) in Japan is high, with an estimated 25,300,000 affected individuals.

OBJECTIVE:

The purpose of this study was to clarify the characteristics of knee osteoarthritis by comparing differences between patients with knee osteoarthritis and healthy elderly individuals with respect to alignment of the pelvis and lower extremities and range of motion.

METHODS:

Twenty-six women (13 with medial knee osteoarthritis and 13 healthy elderly) participated in this study. Pelvic tilt, knee extension angle, femoro-tibial angle, quadriceps angle, navicular drop, and leg-heel alignment were measured. In addition, the range of motion was measured at the hip, knee, and ankle joints.

RESULTS:

Patients with knee osteoarthritis showed a posterior pelvic tilt, knee flexion, varus, and foot pronation alignment compared to healthy subjects. The range of motion for hip extension, adduction, knee flexion, extension, and ankle dorsiflexion was significantly smaller while the range of motion for eversion was significantly larger in the knee osteoarthritis group.

CONCLUSION:

People with medial knee OA have different static alignment and ROM compared to those without knee OA. The results clarify the comprehensive characteristics of the pelvis and lower extremities in knee osteoarthritis.

Keywords

Knee osteoarthritis range of motion lower extremity Japanese

1. Introduction

The prevalence of radiographic knee osteoarthritis (OA) in Japan is high, with 8,600,000 men and 16,700,000 women aged 40 years and older estimated to be affected [1]. The most common deformity in knee OA is varus deformation [2] which is caused by a change in knee alignment. This change of alignment is due to cartilage loss and incident cartilage damage. If such alignment continues for a long period, it can lead to further deformation [3]. Therefore, it is necessary to modify the alignment abnormality. Knee OA also affects the hip and ankle, causing pain and a reduced range of motion (ROM), with subsequent functional decline [4, 5]. Therefore, it is necessary to pay attention not only to the knee in knee OA, but also to the hip and ankle.

Only a few studies to date have evaluated alignment in knee OA. It has been reported that varus or valgus alignment is associated with a reduction in the risk of subsequent cartilage loss [6] and incident cartilage damage [7], and influences the risk of incident and progressive knee OA [3]. These results support the idea that knee alignment is associated with risk for the initial development of knee OA. However, to the best of our knowledge, no reported study has compared the alignment of the pelvis and lower extremities as well as the ROM between patients with knee OA and healthy elderly individuals. Elucidating these factors may contribute to the future development of physical therapy interventions for knee OA and the development of physical therapy interventions to prevent the occurrence of knee OA. The purpose of this study was to compare the alignment of the pelvis and lower extremities as well as the ROM between patients with knee OA and healthy elderly individuals in order to reveal the characteristics of knee OA.

2. Materials and methods

2.1 Subjects

All subjects were females with bilateral medial knee OA (Kellgren and Lawrence grade $\geqslant$ 2). The inclusion criteria were evidence of narrowing of the medial tibiofemoral joint space, complaint of pain on the medial side of the knee, and diagnosis of medial knee OA. Exclusion criteria included bone fracture, hip and/or ankle OA with knee OA, and nerve symptoms. Thirteen elderly women with medial knee OA were included in the knee OA group and 13 healthy elderly women were included in the control group. The knee OA group included individuals that were within five years of the initial diagnosis.

Following an explanation of the experimental protocol, all participants provided written informed consent, and the study was performed in accordance with the Declaration of Helsinki. This study was approved by the Ethics Committee of Tokyo Metropolitan University (number: 11038).

2.2 Measurements

2.2.1 Alignment

Pelvic tilt, knee extension angle, femoro-tibial angle (FTA), quadriceps angle, navicular drop (ND), and leg-heel alignment (LHA) were measured. An image of the static standing posture was taken using a single lens reflex camera (Canon EOS Kiss X4).

The camera was fixed at a 10 m distance from the subjects; the distance was recommended by an expert in the field of Silhouette measurement, on the basis that this setting yields the least error. Silhouette measurement software ver 4.0 (Medic Engineering Co., Ltd.) was utilized to analyze the images. Using the same methods as previously published [8], the landmarks required for measurement were arranged to be visible on the images. To accomplish this, a 6-mm reflective marker with a seat (VACC-V1611, Inter-Riha Co., Ltd.) was attached to the bilateral anterior superior iliac spine and posterior superior iliac spine. The actual distance between the bilateral greater trochanters and (1) the center of the lateral knee joint space, (2) the center of the patella, and (3) the center of the medial and lateral knee joint space were measured, and the distance between the midpoints and the tuberositas tibiae, medial, and lateral malleolus was measured. Then, 3-mm round-shape stickers (A-ONE G.K.) were attached to the midpoints and the lateral malleolus (Fig. 1). The alignment-related measurements were performed by same examiner (MM) who was a physiotherapist with approximately 10 years of experience at the time of measurement.

Figure 1.

Alignment-related measurements of the pelvis and lower extremity. The femoro-tibial angle (FTA) and quadriceps angle (Q-angle) are depicted in the frontal plane; the pelvic angle and knee extension angle are depicted in the sagittal plane.

Prior to filming the posture, the positions of the camera and subject were calibrated. A 45-cm square plate was hung 10 m away from the lens of a single-lens reflex camera fixed on a tripod, with its upper side adjusted to be parallel to the floor using a level gauge. Then, the posture was filmed with deep field depth adjusting the f-stop and the shutter speed to 13 Av and 1/30 s, respectively, to focus on an image in both front and back. Obtained images were downloaded to the image analysis software to confirm that the length of every plate side was identical (45 cm), completing the calibration.

Once calibration was completed, the subject was instructed to stand barefoot on a rotating table 40.5 cm in diameter (Abera Corporation) which was placed 10 m away from the lens of the single-lens reflex camera. The subject was verbally instructed to stand naturally after stepping on the table. The anterior and lateral sides of the subject were filmed under these conditions (Fig. 1). An examiner rotated the table slowly to avoid fluttering when the filming direction was changed so that the posture of the subject could be stabilized as much as possible.

The pelvic angle, knee extension angle, FTA, and Q-angle were analyzed using the images. Using the lateral image, the angle between a line connecting the anterior superior iliac spine with the posterior superior iliac spine and a horizontal line was measured as the pelvic angle ( ${}^{\circ}$ ) [9, 10, 11], and the angle made by the greater trochanter, the center of the lateral knee joint space, and the lateral malleolus was measured as the knee extension angle ( ${}^{\circ}$ ) [11]. If the three points were in a straight line, it was regarded as 180 ${}^{\circ}$ . Using the anterior images, FTA ( ${}^{\circ}$ ) was determined by measuring the angle made by the midpoint connecting the anterior superior iliac spine and the center of the medial and lateral knee joint space and the midpoint connecting the medial and lateral malleolus [11]. Using the anterior images, the angle made by the anterior superior iliac spine, the center of the patella, and the tuberositas tibiae was measured as the Q-angle ( ${}^{\circ}$ ) (Fig. 1).

Figure 2.

Navicular drop. The distance between the floor and the navicular tuberosity was measured in two positions (non-weight-bearing and weight-bearing).

Figure 3.

Leg-heel alignment. The angle made by the bisectors of the lower extremity and calcaneus was measured using a goniometer while keeping the subject in a natural standing position.

The actual values of the ND and LHA were measured (Figs 2 and 3). For ND (mm), the distance from the floor to the navicular tuberosity was measured while keeping the subject in a sitting position with the lower extremities drooped, plantar dorsiflexion of the ankle joint at 0 ${}^{\circ}$ , and the planta contacted to the floor to avoid a load (non-load) [12, 13]. Next, the distance from the floor to the navicular tuberosity was measured while keeping the subject in a standing position with equal loading on both lower extremities (loaded). Then, the ND value was determined by calculating the difference (non-load – loaded). A self-made measuring apparatus connecting a scale (Japanese Industrial Standard) with an L-shaped bracket was used for the measurement of the ND. LHA (o) was determined by measuring the angle made by the bisectors of the lower extremity and calcaneus using a goniometer while keeping the subject in a natural standing position. A positive value was regarded as calcaneus valgus [11].

2.2.2 ROM

The ROM was measured for hip flexion, abduction, adduction, external rotation, internal rotation, knee flexion, extension in the supine position, hip extension in the prone position, ankle dorsiflexion, plantar dorsiflexion, eversion, and inversion in the sitting position.

Eversion and inversion were measured as mainly subtalar joint motion without accompanying plantar dorsiflexion motion. They were measured in 1 ${}^{\circ}$ increments with a goniometer (the University of Tokyo type) with level gauges on both arms. Each item was measured as previously described [14]. Every measurement item was measured once by the same examiner (MM) who moved the subject’s joints to the maximum ROM while another examiner kept the subject’s position stable.

2.3 Statistical analysis

Independent t-tests for age, height, mass, body mass index (BMI), alignment-related measurements and ROM were performed. The alpha level was set at 0.05. All statics were calculated using SPSS version 21 (IBM Corp., Tokyo, Japan).

Table 1
Characteristics of the subjects

	OA	Healthy
N, people (knees)	13 (26)	13 (26)
Age, years (range)	73.1 (65–79)	70.3 (64–78)
Height (cm)	149.2 $\pm$ 5.4	151.9 $\pm$ 4.4
Mass (kg) ${}^{*}$	57.7 $\pm$ 5.5	52.2 $\pm$ 3.7
BMI (kg/m ${}^{2}$ ) ${}^{*}$	26.0 $\pm$ 2.2	22.7 $\pm$ 1.8
Kellgren and Lawrence grade
I	0
II	8
III	5
IV	0

BMI $=$ body mass index. Height, mass, and BMI values indicate mean $\pm$ standard deviation. ${}^{*}$ : $P<$ 0.05.

3. Results

The characteristics of the subjects are shown in Table 1. Age and height were not significantly different between the two groups. The knee OA group demonstrated significantly larger mass and BMI. Tables 2 and 3 show the results for alignment-related measurements and ROM, respectively. The knee OA group showed a significantly smaller pelvic angle and knee extension angle. The FTA, ND, and LHA were significantly greater in the knee OA group. The ROM for hip extension, adduction, knee flexion, extension, and ankle dorsiflexion was significantly smaller in the knee OA group while the ROM for hip abduction was significantly larger in the knee OA group.

Table 2
Results of the alignment of the pelvis and lower extremities

	OA		Healthy		95% confidence intervals
Pelvic angle ( ${}^{\circ}$ ) ${}^{*}$	12.8	$\pm$ 3.3	15.5	$\pm$ 2.4	–5.16– $-$ 0.25
Knee extension angle ( ${}^{\circ}$ ) ${}^{*}$	173.2	$\pm$ 6.5	179.6	$\pm$ 2.8	–10.58– $-$ 2.06
FTA ( ${}^{\circ}$ ) ${}^{*}$	178.7	$\pm$ 3.4	174.3	$\pm$ 1.8	2.01–6.66
ND (mm) ${}^{*}$	10.5	$\pm$ 3.7	7.3	$\pm$ 1.9	0.73–5.77
LHA ( ${}^{\circ}$ ) ${}^{*}$	9.3	$\pm$ 3.2	6.4	$\pm$ 1.7	0.70–5.13
Q-angle	18.3	$\pm$ 5.7	19.8	$\pm$ 5.8	–6.31–3.44

FTA: Femoro-Tibial Angle, ND: Navicular Drop, LHA: Leg-Heel Alignment, Q-angle: Quadriceps angle. Values indicate mean $\pm$ standard deviation. ${}^{*}$ : $P<$ 0.05.

Table 3

Results of the ROM of the hip, knee, and ankle

	OA		Healthy		95% confidence intervals
Hip flexion	132.4	$\pm$ 7.4	132.9	$\pm$ 7.5	–6.78–5.78
Extension ${}^{*}$	19.6	$\pm$ 5.7	26.5	$\pm$ 2.8	–10.70– $-$ 3.13
Abduction ${}^{*}$	38.5	$\pm$ 6.2	33.8	$\pm$ 3.2	0.40–8.94
Adduction ${}^{*}$	7.9	$\pm$ 3.0	11.2	$\pm$ 3.5	–6.00– $-$ 0.50
External rotation	46.5	$\pm$ 9.5	52.1	$\pm$ 8.0	–13.03–1.87
Internal rotation	21.1	$\pm$ 7.8	19.3	$\pm$ 8.5	–5.08–8.74
External rotation (prone)	43.2	$\pm$ 5.4	38.0	$\pm$ 8.1	–0.67–11.00
Internal rotation (prone)	36.9	$\pm$ 8.3	35.8	$\pm$ 11.0	–7.06–9.39
Knee flexion*	142.1	$\pm$ 8.7	154.3	$\pm$ 2.3	–17.86– $-$ 6.64
Extension ${}^{*}$	$-$ 4.3	$\pm$ 6.0	2.2	$\pm$ 4.9	–11.03– $-$ 1.81
Ankle dorsiflexion ${}^{*}$	22.5	$\pm$ 5.3	28.3	$\pm$ 6.9	–10.95– $-$ 0.55
Plantar flexion	54.8	$\pm$ 8.1	54.5	$\pm$ 6.0	–5.71–6.38
Eversion	13.0	$\pm$ 6.5	11.1	$\pm$ 4.4	–2.77–6.60
Inversion	41.4	$\pm$ 7.4	42.3	$\pm$ 9.0	–7.86–6.02

Values indicate mean $\pm$ standard deviation. The unit of measurement for all items is ${}^{\circ}$ . ${}^{*}$ : $P<$ 0.05.

4. Discussion

We compared the knee/lower extremity alignment and ROM between elderly women with knee OA and healthy elderly women. The results demonstrated that patients with knee OA show alterations in alignment, including a posterior pelvic tilt, knee flexion, varus alignment, and foot pronation. Moreover, it was revealed that the ROM was smaller for hip extension, adduction, knee flexion, extension, and ankle dorsiflexion, and larger for hip abduction in patients with knee OA compared to healthy subjects. Watanabe et al. [15] reported that knee flexion contracture was a relevant factor in knee OA. Specifically, patients with knee OA are likely to show a knee flexed position. In the current study, patients in the knee OA group also showed more of a knee flexed position compared to those in the healthy group, and they had reduced ROM of knee extension. Therefore, the knee flexed position can be considered as one of the typical alignments in knee OA.

In the present study, the ND was 10.5 mm in the knee OA group. Loudon et al. [16] described the supinated position, neutral position, and pronated position as when the ND was less than 6 mm, between 6 and 9 mm, and more than 9 mm, respectively. Thus, the knee OA group in the current study showed a pronated position. In a previous study, it is reported that due to subtalar pronation, there was an increase in the internal rotation of the lower legs and thighs, and anterior pelvic tilt [17]. This demonstrated the so-called kinematic chain spread ascending from the ankle, and subtalar pronation was accompanied by knee valgus in healthy subjects. On the other hand, it can also be considered that subtalar supination causes knee varus. In a previous study, foot pronation has been shown to be more remarkable in knee OA [4], and the pronation moment of the subtalar joint has been shown to be increased in the knee varus during walking [18]. These findings suggest that knee varus, such as that seen in medial knee OA, is accompanied by foot pronation. Levinger et al. [4] suggested that increased foot pronation could potentially reduce the adduction moment by shifting the center of pressure medially, compensating for the load when contacting the planta with the floor by foot pronation. The same finding was also observed in the knee OA group in this study.

As alignment in the knee OA group showed knee varus position, it can be assumed that the hip is in an abducted position. Joint contracture due to a decreased ROM leads to shortening of the periarticular connective tissue and muscle [19]. Persistence of such an alignment possibly leads to a reduction in hip adduction ROM and increased hip abduction, because extensibility of the hip abductor muscles is in a shortened position and extends the hip adductor. Moreover, alignment of the knee OA group in the current study, which showed a posterior pelvic tilt and knee flexion position, caused reduction of hip extension and knee flexion ROM because the rectus femoris muscle, which is a biarticular muscle, was in the tension state to maintain the standing position. In a posterior pelvic tilt and knee flexion position, the hamstrings muscle is shortened. This is also surmised to be one of the factors that contribute to a smaller knee extension ROM. In knee OA, the reduction of knee flexion and extension ROM is associated with physical activities [20]. In this study, the knee OA group demonstrated reduced ROM for knee flexion and extension. Interventions are necessary to correct these reductions. Stretching has been shown to increase ROM, speed of walking, and knee joint angle during walking [21, 22], with improved pain [22]. Intervention research is needed to improve ROM reductions in knee OA.

We previously investigated alignment changes due to aging in healthy subjects aged 20 to 70 years old [11]. The results demonstrated that the alignment of women changed to a posterior pelvic tilt, hip external rotation, knee flexion, and foot pronation with age. The results of the present study demonstrated that the alignment of patients in the knee OA group showed a greater posterior pelvic tilt, knee flexion and varus, and foot pronated position compared to the healthy group. Such alignment in the knee OA group can be considered as a consequence of alignment change with age in healthy subjects. Therefore, alignment changes with age in healthy subjects may come close to the alignment of patients with medial knee OA. From this study, it cannot be determined whether this change causes the knee OA. It is necessary to examine basic variables such as muscle strength, because various factors are associated with alignment changes. Moreover, longitudinal investigations of healthy elderly individuals are necessary to determine factors related to the occurrence of knee OA, as well as investigations of differences between individuals with and without knee OA.

This study has some limitations worth noting. First, all study subjects were Japanese, and this may have influenced alignment and ROM because sitting straight (called “Seiza”) and sitting on the floor are part of Japanese lifestyle habits. Thus, the basic data for alignment and ROM may not be directly comparable to data from other countries. However, it is meaningful to present characteristics of alignment and ROM in knee OA among the Japanese population. Second, the examiner and image readers were not blinded. For alignment, markers and seals were attached to similar landmarks in healthy subjects. In addition, the limb was properly moved until the end of the ROM, and was then measured; therefore, this issue was minimized. Although there was a significant difference in ROM of hip adduction, it was as small as 3 ${}^{\circ}$ . Even in healthy subjects, ROM for hip joint adduction is minimal. In clinical practice we have encountered several knee OA patients whose hip adduction ROM was reduced. However, it is possible that the 3 ${}^{\circ}$ difference might count as a measurement error of the goniometer. Finally, we did not consider the activity level of the subjects, and this should be evaluated in future studies.

5. Conclusion

We compared the pelvic/lower extremity alignment and ROM between patients with medial knee OA and healthy elderly subjects. Posterior pelvic tilt, knee varus and flexion, and foot pronated position were more pronounced in the knee OA group. The ROM was smaller for hip extension and adduction, knee flexion and extension, and ankle dorsiflexion while the ROM for hip abduction was larger in the knee OA group. The findings of this study can contribute to the development of physical therapy intervention methods for knee OA and the development of physical therapy intervention methods to prevent knee OA occurrence.

Footnotes

Acknowledgments

The authors thank Mizuo Shinoda for his cooperation, and Yoji Shimizu, Ryouji Sunaga, and Etsuki Tomita for their assistance with data collection.

Conflict of interest

None to report.

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Pelvis/lower extremity alignment and range of motion in knee osteoarthritis: A case-control study in elderly Japanese women

Abstract

BACKGROUND:

OBJECTIVE:

METHODS:

RESULTS:

CONCLUSION:

Keywords

1. Introduction

2. Materials and methods

2.1 Subjects

2.2 Measurements

2.2.1 Alignment

2.3 Statistical analysis

Table 1 Characteristics of the subjects

Table 2 Results of the alignment of the pelvis and lower extremities

5. Conclusion

Footnotes

Acknowledgments

Conflict of interest

References

Table 1
Characteristics of the subjects

Table 2
Results of the alignment of the pelvis and lower extremities