Effect of obesity on knee joint biomechanics during gait in young adults

Figures & data

Table 1. Anthropometrics, Lower Extremity Functional Scores (LEFS), and self-selected natural walking speed means and standard deviations (SD) for the obese and healthy participant groups

Descriptive statistics
	Obese mean (SD)	Healthy mean (SD)	Mean diff	p-value
Age	23.5 (3.3)	23.5 (2.2)	0.01	0.978
Mass (kg)	104.5 (20.0)	69.1 (6.0)	−35.5	0.001^*
Height (m)	1.71 (0.06)	1.72 (0.06)	0.01	0.447
BMI (kg/m^2)	35.5 (5.7)	23.3 (1.5)	−12.2	0.000^*
Waist (m)	1.16 (0.16)	0.79 (0.06)	−0.27	0.000^*
Thigh (m)	0.68 (0.05)	0.55 (0.02)	−0.13	0.000^*
Shank (m)	0.44 (0.02)	0.37 (0.02)	−0.07	0.000^*
LEFS	73.9 (3.9)	78.3 (2.3)	4.4	0.054
Natural gait speed (m/s)	1.25 (0.15)	1.55 (0.18)	0.3	0.013^*

Notes: The terms waist, thigh, and shank refer to the circumference of each of these segments. The LEFS questionnaire was scored out of a total of 80.

^* Significant mean differences in dependent t-tests at p < 0.05.

Figure 1. The knee adduction moment and CKAL of the two removed obese subjects, referred to as S01 and S04 compared to the mean obese and healthy-weight group knee adduction moments and CKAL.

Notes: The adduction waveforms of both S01 and S04 do not conform to typical knee adduction moments seen in individuals without musculoskeletal pathology. The CKAL for S04 and S01 is calculated from the self-selected natural walking speed, and is expressed in kNm s.

Table 2. Results for the knee angles and moments for obese and healthy-weight participants at the self-selected speed condition

		Angles (degrees)					Moments (Nm)
Plane	Parameter	Obese mean (SD)	Healthy mean (SD)	Mean diff	p-value	CI	Obese mean (SD)	Healthy mean (SD)	Mean diff	p-value	CI
Adduction	Peak	3.5 (2.5)	−0.1 (2.4)	−3.5	0.002*	−3.5 ± 12.03	40.2 (23.3)	29.9 (6.5)	−10.2	0.12	−10.2 ± 13.1
Abduction	Peak	−4.0 (3.1)	−8.3 (3.5)	−4.3	0.003*	−4.3 ± 2.6	−13.7 (10.1)	−9.7 (5.2)	4.0	0.13	4.0 ± 5.3
	Range	7.5 (2.5)	8.2 (3.6)	−0.7	0.510	−0.7 ± 2.2	53.9 (31.9)	39.7 (5.6)	−14.2	0.07	−14.2 ± 15.5
Flexion	Peak	45.7 (3.9)	46.4 (5.5)	−0.7	0.595	−0.7 ± 2.2	64.9 (43.8)	66.1 (19.9)	−1.1	0.92	−1.1 ± 22.8
Extension	Peak	−0.1 (3.7)	4.0 (6.1)	−4.1	0.044*	−0.7 ± 2.2	−44.4 (21.3)	−26.9 (6.9)	−17.4	0.005^*	−17.4 ± 11.4
	Range	45.9 (4.9)	42.4 (2.96)	3.5	0.027*	3.5 ± 3.1	109.4 (46.1)	93.0 (22.7)	16.4	0.17	16.4 ± 24.1
Medial rotation	Peak	4.9 (9.3)	5.6 (3.1)	−0.7	0.787	−0.7 ± 5.4	8.7 (6.2)	10.2 (3.9)	−1.5	0.39	−1.5 ± 3.6
Lateral rotation	Peak	−4.6 (8.9)	−5.9 (6.7)	1.3	0.641	1.3 ± 5.8	−7.1 (5.1)	−2.3 (1.6)	−4.8	0.005^*	−4.8 ± 3.1
	Range	9.6 (2.3)	11.6 (5.0)	−2.1	0.114	−2.1 ± 2.7	15.8 (6.4)	12.5 (3.8)	3.3	0.06	3.3 ± 3.5

Notes: In the self-selected speed condition, the three speeds of fast, natural, and slow were included to determine mean values. CI represents the confidence intervals associated with each test statistic.

^* Significant mean differences at p < 0.05

Figure 2. Average (A) adduction/abduction, (B) flexion/extension, (C) internal/external rotation angles, (D) adduction/abduction, (E) flexion/extension, (F) internal/external rotation moment waveforms for both participant groups at the combined self-selected speed condition.

Notes: In the self-selected speed condition, mean curves were determined using the three speeds of fast, self-selected, and slow. The healthy-weight group is represented by the solid line and the obese group is represented by the dotted line. A positive value on the vertical axis represents an adduction, flexion or internal rotation moment. Significant mean differences between groups are indicated by an asterisk where they occurred in the gait cycle.

Table 3. Results for the knee angles and moments for obese and healthy-weight participants at the matched speed condition

		Angles (degrees)					Moments (Nm)
Plane	Parameter	Obese mean (SD)	Healthy mean (SD)	Mean diff	p-value	CI	Obese mean (SD)	Healthy mean (SD)	Mean diff	p-value	CI
Adduction	Peak	3.7 (2.7)	−0.3 (2.1)	−3.4	0.052	−3.5 ± 3.6	39.6 (21.9)	25.9 (7.6)	−13.6	0.183	−13.6 ± 22.6
Abduction	Peak	−3.9 (3.1)	−7.5 (3.3)	−3.6	0.148	−4.3 ± 6.5	−13.0 (9.3)	−9.1 (5.1)	3.9	0.338	3.9 ± 9.46
	Range	7.6 (2.8)	7.1 (3.4)	−0.5	0.828	−0.7 ± 7.9	52.6 (29.5)	35.0 (8.1)	−17.6	0.166	−17.6 ± 27.9
Flexion	Peak	45.6 (4.1)	46.2 (7.3)	0.6	0.789	−0.7 ± 6.4	61.4 (40.2)	47.5 (10.7)	13.9	0.386	13.9 ± 37.6
Extension	Peak	−0.4 (3.3)	2.1 (4.7)	2.5	0.364	−4.1 ± 10.6	−44.3 (21.2)	−26.9 (5.4)	−17.3	0.125	−17.3 ± 24.2
	Range	46.1 (5.5)	44.1 (3.8)	−2.0	0.463	3.5 ± 11.3	105.6 (40.6)	74.4 (15.3)	31.2	0.081	31.2 ± 36.8
Medial Rotation	Peak	5.2 (8.8)	5.1 (4.7)	−0.1	0.977	−0.7 ± 59.4	8.3 (6.3)	9.7 (4.9)	−1.4	0.669	−1.4 ± 7.9
Lateral Rotation	Peak	−4.1 (8.4)	−6.8 (8.0)	−2.7	0.590	1.3 ± 5.8	−4.2 (5.9)	−2.4 (0.8)	−1.7	0.105	−1.7 ± 2.2
	Range	9.3 (1.6)	11.9 (5.3)	2.6	0.316	−2.1 ± 4.8	9.3 (8.1)	12.2 (4.9)	−2.8	0.272	−2.8 ± 5.8

Notes: In the matched speed condition, the healthy-weight participants walked at the self-selected natural speed of their matched obese participant. CI represents the confidence intervals associated with each test statistic.

Figure 3. Average (A) adduction/abduction, (B) flexion/extension, (C) internal/external rotation angles, (D) adduction/abduction, (E) flexion/extension, (F) internal/external rotation moment waveforms for both participant groups at the matched speed condition.

Notes: The matched speed mean curves were determined using the self-selected speed for the obese group and the matched speed for the healthy-weight group. The healthy-weight group is represented by the solid line and the obese group is represented by the dotted line. A positive value on the vertical axis represents an adduction, flexion or internal rotation moment. Significant mean differences between groups are indicated by an asterisk where they occurred in the gait cycle.

Table 4. Group differences in stance duration (s), steps per day, moment impulse (Nm s), and cumulative knee adductor load (kNm s)

	Obese mean (SD)	Healthy mean (SD)	Mean difference	p-value	CI
Stance duration	0.67 (0.064)	0.61 (0.069)	−0.06	0.003*	−0.06 ± 0.03
Steps/day	7228.7 (2478.1)	8148.4 (1389.6)	571.1	0.591	571.1 ± 2558.28
Moment impulse	11.93 (5.84)	8.45 (2.64)	−3.48	0.049*	−3.48 ± 3.46
CKAL	43.61 (20.88)	30.65 (13.38)	−12.96	0.025*	−12.96 ± 10.53

Note: CI represents the confidence interval associated with the test statistic.

^* Significant group differences at p < 0.05.

Table 5. The marker-based knee alignment of the two obese subjects removed from the data analysis during their self-selected natural walking speed

	Obese	Healthy-weight	S01	S04
Knee alignment (degrees)	−3.56	0.324	−9.459	−10.297

Note: The alignment of both subjects is valgus, and different from the obese mean.