Heel kicking exercise rapidly improves pain and function in patients with acute lateral ankle sprain: a randomized controlled trial

Abstract

Background

Ankle sprain is one of the common traumatic injuries in daily life, and PRICE (protection, rest, ice, compression pressure bandaging, elevation of the affected limb) principle is routinely recommended at its early stage. In traditional Chinese medicine (TCM), bone-setting technique (BST) can quickly relieve ankle pain and improve walking function, but physicians require high skills and physical strength. In this study, we designed an exercise—heel kicking exercise (HKE) based on the principles and methods of BST. This study aims to observe its true efficacy and safety.

Methods

68 patients (18–45 years old) with grade I and II lateral ankle sprain within 48 h were recruited from TCM hospital affiliated to Guangzhou medical university and 60 cases meeting the criteria were enrolled and randomized into control group and intervention group (30 cases separately). The patients in both groups were treated with the PRICE and ankle pump exercise, and the ones in intervention group added heel kicking exercise (HKE). The visual analogue scale (VAS) for pain, swelling degree, and American orthopedic foot & ankle society ankle-hindfoot scale (AOFAS) score before and after the intervention (within 4 W), and Karlsson score (the 26th week follow-up) were measured.

Results

Before treatment, there were no significant differences in VAS scores, swelling degrees and AOFAS scores between two groups. During the treatment for 4 weeks, VAS scores and swelling degrees of the patients in both groups gradually decreased, and the AOFAS score gradually increased (p < 0.01). In addition, patients in the intervention group were observed to get a quicker pain reliever, swelling subsiding, and ankle function restore than those in control group at most of time points of observation (1st d, 3rd d, 1st w, 2nd w, 4th w) (p < 0.05, p < 0.01). But there was no significant difference in Karlsson scores between two groups at the 26th week follow-up.

Conclusions

HKE is a method designed to provide rapid movement rehabilitation for patients with ankle sprains, which can be used as one of its basic treatments.

Trial registration

This study was registered in China Clinical Trial Center (NO. ChiCTR2300073709). Trial registration date: August 16th 2022.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-025-08881-9.

Introduction

Acute ankle sprain is the most common trauma of the human musculoskeletal system in daily life, and the re-sprain rates estimated to be 70% [1–4]. Many studies have documented that Up to 73% of patients experienced at least one recurrence of ankle twist after one acute ankle sprain, and 30–70% of acute ankle sprains with inadequate treatment eventually develop into chronic ankle instability [5, 6]. Conservative treatment is mainly used for Grade I and II ankle sprain, and the acute stage should be treated according to the principle of PRICE (protection, rest, ice, compression pressure bandaging, elevation of the affected limb) and the ankle pump exercise can promote swelling reduction and function recovery [7–10]. Currently, the conservative treatment plan for acute ankle sprains involves 3 phases rehabilitation programs, Phase 1 aims to limit the degree of injury, phase 2 focuses on restoring the joint range of motion and strength, and phase 3 concentrates on agility and endurance [11]. And some studies have also shown that early stretch functional exercise can accelerate the recovery of ankle sprain function for Grade I and II ankle sprains [12–17].

Orthopedics of traditional Chinese medicine (TCM) believes that ankle sprain is a typical case of “mild malposition of bone and joint, tendon off position (MMBJTP)” [18], and early bone-setting manipulation (BSM) of TCM can promote rapid recovery and reduce the incidence of ankle instability and chronic pain [19–21]. The space between bones is called as a suture. The slight displacement of bones leads to the change of space between bones, which is named as mild malposition of bone and joint [18]. There are the microanatomical position changes of the joint, local pain and restricted movement when mild malposition of bone and joint occurs because of the influence of external force [18]. And the degree of mild malposition of bone and joint is significantly less than subluxation, and there are no obvious signs on the image [22]. Tendon which belongs to the basic concept in traditional Chinese medicine, is related to fibrous connective tissues with biomechanical properties such as muscles, tendons, ligaments, joint capsules and intervertebral discs. Tendon off position refers to the abnormal change of the morphological structure, functional state and position of the tendon, which is caused by indirect violence or chronic cumulative external force [18].

Some theoretical foundations have also been provided for MMBJTP for some years. Huxley et al. reported the ultrastructure of muscle fibers under an electron microscope, laying a structural foundation for explaining the principle of muscle contraction [23, 24]. The proposal of the sliding filament theory and the cross-bridge theory [25] has enabled us to understand and analyze tendon off position at the microscopic level. When muscles are overloaded or contract continuously, abnormal mechanical stress causes changes in the spatial conformation of myofibrils [26], resulting in a lateral redistribution of muscle fibers, which in turn hinders the sliding of thick and thin filaments and leads to their entrapment [27]. Yang et al. [28] established an animal model of tendon off position by applying static loads to the upper limb muscles of rats to cause continuous isometric contraction of the upper limb muscles. The results showed that after two weeks of modeling, the upper limbs of the rats exhibited typical symptoms of tendon off position. Observations of the myofibrils in the upper limb muscles revealed structural abnormalities such as Z-shaped distortions and blurred light and dark boundaries. Therefore, tendon off position is not only manifested in appearance but also has significant structural changes at the microscopic level. Lateral ankle sprains usually involve excessive inversion-internal rotation, which leads to mild malposition of bone and joint, tendon off position.

Traditional bone-setting manipulations, which may quickly treat the ankle sprain and significantly reduce complications, not only pay high attention to fracture reduction, but also to sinew-regulating and soft tissues protection [29]. But when the patient is too fat and the orthopedists’ strength is relatively insufficient, it is difficult to complete the bone setting.

Heel kicking exercise (HKE) which we designed, is derived from the traditional Chinese medicine theory, such as mild malposition of bone and joint, tendon off position (MMBJTP) and BSM. HKE which is a kind of functional bone-setting therapy, lengthens the soft tissue around the ankle and widens the space of the ankle joint, and then the talus retracts to the ankle point automatically, completing the process of closing and leaving first, so as to achieve the purpose of automatically correcting the slight dislocation of the ankle joint. However, there are no data on the effect of HKE on the acute lateral ankle sprain. The present study aimed to observe the effect of HKE on pain reduction and function recovery of Grade I and II acute lateral ankle sprains, and to evaluate its safety.

Methods

Study design

In this randomized, controlled, parallel clinical trial, all subjects developed an acute lateral ankle sprain (grade I and II) within 48 h prior to enrollment and were randomized into control group and intervention group. All patients were treated with the PRICE and ankle pump exercise, and the ones in the intervention group were performed with HKE at the same time. The 10-cm pain visual analogue scale (VAS) scores and American Orthopaedic Foot & Ankle Society ankle-hind foot (AOFAS) scores were measured at the time points when patients were treated after Baseline, 1d, 3ds, 1w, 2ws and 4ws treatment, and swelling degrees were measured when patients were treated after Baseline, 3ds, 1w, 2ws, 4ws treatment and ankle function by the Karlsson scores were assessed at the 26th week. This study was approved by the Medical Ethics Committee of TCM hospital affiliated to Guangzhou medical university in China (the Ethics Committee’s ID:2022NK036).

Sample size evaluation

The experimental sample was determined through G power analysis and calculation (version 3.1.9.6). Heel kicking exercises were first used in patients with ankle sprains, so there is a lack of literature on sample size estimation. Based on the literature using PRICE as the control group for short-term (3–7 days) treatment [30, 31], we determined an effect size of 0.8–0.85, with a two-tailed test, and a significant alpha level equal of 0.05 and 80% power. This yielded a sample size of 23–26 patients per group. Considering a conservative dropout rate of approximately 10%, we need to enroll at least 57 patients in the study.

Participants

68 outpatients with acute lateral ankle sprain, participated in this experimental procedure (27 women and 32 men,31.29 ± 11.33 years, 168.20 ± 8.20 cm, 64.62 ± 11.29 kg), from traditional Chinese medicine hospital affiliated to Guangzhou medical university during the period of September 2022 to December 2023, Diagnostic criteria were: (1) has a history of lateral ankle sprain or injury; (2) pain, swelling and dysfunction of the injured part; (3) local examination revealed swelling, obvious tenderness, muscle spasm, stiffness and lack of softness in the affected part; (4) X-ray examination found no fracture or dislocation [32]. Inclusion criteria were: (1) 18–45 years old; (2) definite history of acute sprain of lateral ankle (within 48 h), causing swelling, pain and dysfunction of ankle; (3) good compliance and willingness to complete diagnosis and treatment; (4) Oswestry Disability Index (BMI) (18–25); (5) sign the informed consent form. Exclusion criteria were: (1) Serious lower-extremity injuries of the last 6 months (e.g., fractures, ligament ruptures); (2) ankle ligament rupture (Grade III) (mechanical instability diagnosed by a positive anterior drawer or inversion stress test [33] or ultrasound); (3) physical disability, psychosis, severe cardiac and lung failure, etc. cannot cooperate with observers for treatment; (4) Sprained ankle joint of both lower limbs, or medial and lateral injuries of ankle joint of one lower limb. Participants in the control group were treated with the routine PRICE treatment and ankle pump exercise (50 times at a time, thrice daily). The intervention group was treated with HKE and PRICE plus ankle pump exercise.

Randomization

All the participants were randomly assigned to the control and the intervention group at a ratio of 1:1. 60 random number sequences were produced from 999 numbers through an online random number generator, the generated random numbers were written on paper strips and sealed in envelopes. Even-numbered patients were assigned to the control group, while Odd-numbered patients were assigned to the intervention group.

Ankle pump exercise

Lie flat on the bed, stretching your lower limbs naturally, slowly raise your toes to the ankle joint, and relax naturally after ten seconds. This is a cycle. Relax for 10 s and then proceed to the next cycle, each time for a total of 50 cycles, three times a day.

Heel kicking exercises (HKE)

Patients stand firmly against a wall, standing on a healthy limb, lifting the affected leg, with flattening the thigh of the affected limb and bending the knee joint, forming an angle of 70–80 degrees between the lower leg and the thigh. Subsequently, the ankle joint of the affected leg achieves maximal dorsiflexion, and then pushes forcefully the affected heel forward and downward until the angle between legs reaches 10–15 degrees. The ankle joint ends in dorsiflexion, with the healthy leg kept straight at all courses. (Fig. 1). When the ankle joint is sprained, the patient immediately kicks the heel 6 to 10 times, next the patients are asked to walk on flat ground and then squat down, when they felt the pain is relieved and the squatting exercise is improved significantly, HKE exercise stops. In the following four weeks, HKE was performed once a day, 3–4 movements each time. If you feel joint stiff or interlocking when you walk, add it once or twice.

Fig. 1.

Image of Heel kicking exercises

Outcome measurements

The primary outcome measures were visual analog scale (VAS) score for pain, swelling degree, and American orthopedic foot & ankle society ankle-hind foot (AOFAS) score.

Pain was evaluated using a 10-cm visual analogue scale (VAS), with one end marked “no pain” and the other end marked “the most severe pain imaginable”. This form of assessment is considered the most reliable because it has high repeatability when used repeatedly in the same patient [34]. VAS scores were recorded before treatment and 1 day, 3 days, 1 week, 2 weeks and 4 weeks after treatment.

Ankle swelling was measured using a modified version of the figure-of-eight method with a flexible tape [35]. It has been reported that intra and inter-rater reliability is very high using this technique (ICC = 0.99, 95% CI lower limit = 0.98), MDC = 9.6 mm (95% CI). Two designated physicians independently measure the patient’s sprained ankle and healthy ankle. The swelling degree of the ankle joint can be obtained by subtracting the mean value of the healthy ankle from that of the affected ankle. Ankle swelling degrees were recorded before treatment and 3 days, 1 week, 2 weeks and 4 weeks after treatment.

AOFAS scores were recorded before treatment, 1 day, 3 days, 1 week, 2 weeks and 4 weeks after treatment [36], and ankle Karlsson scores were followed up at the 26th week [37].

Statistical analyses

The data were expressed as mean, standard deviation, frequency, and percentage. The baseline parameters between two groups were compared using the independent t test and chi-square test. Kolmogorov-Smirnov and Levene’s tests were carried out to determine normality of the data distribution and homogeneity of variance, respectively, for all outcome measures. One-way repeated measure ANOVA and Bonferroni post hoc tests were used for within-group comparison of the parameters (VAS, AOFAS and edema) across baseline, 1st, 3rd day and 1st, 2nd and 4th week. To compare the parameters between the two groups, the two-way repeated measure ANOVA and the independent t-test were used, while Mann Whitney U test was applied for the Karlsson score at the 26th week follow-up. The alpha level was set at p < 0.05. Data was analyzed using IBM SPSS Statistics for windows (Version 27.0. Armonk, NY: IBM Corp, USA).

Results

The participant flow chart of two groups, including exclusions and losses to follow-up, is demonstrated in Fig. 2. In total, 68 patients interviewed for the study, 60 patients meeting the inclusion criteria were randomized, 30 to the control group and 30 to the intervention group. One participant in the control group added other treatments and hence excluded from the analyses. A total of 59 patients were analyzed, with 29 cases in control group and 30 cases in intervention group. There were no statistical differences in demographic and clinical characteristics of the participants in both groups (Table 1).

Fig. 2.

Flowchart of the study participants

Table 1.

Demographic and clinical characteristics of the participants in both groups

Dependent variables	Control(n = 29) Mean ± SD or n (%)	Intervention(n = 30) Mean ± SD or n (%)	t/χ2	P
Age (Years)	29.90 ± 7.54	32.78 ± 8.81	1.208a	0.232
Gender
Female	13(44.83)	15(50.00)	0.254b	0.691
Male	16(55.17)	15(50.00)
Grade
I	13(44.83)	14 (46.67)	0.020b	0.887
II	16 (55.17)	16 (53.33)
BMI (kg/m²)	22.71 ± 2.57	22.63 ± 1.91	0.118a	0.907
Laterality
Right	18(62.07)	20(66.67)	0.136b	0.712
Left	11(37.93)	10(33.33)
Education level
Low	18(62.07)	19(63.33)	0.010b	0.920
High	11(37.93	11(36.67)
Marital status
Married c	22(75.86)	21(70.00)	0.256b	0.613
Single d	7(24.14)	9(30.00)

^a t test, ^b chi-squared test, ^c included those who cohabit with someone, ^d included the unmarried, divorced, widowed, and separated, n frequency, % percentage, SD standard deviation

Baseline data distribution between control group and intervention group

The results in Table 2 displayed that there were no significant differences(p > 0.05) at baseline of the clinical characteristics of the participants in both groups.

Table 2.

Comparison of the clinical characteristics of the participants in both groups at baseline

Dependent variables	Control(n = 29) Mean ± SD	Intervention(n = 30) Mean ± SD	MD(95% CI)	t	P
VAS	5.03 ± 0.62	5.13 ± 0.31	0.09(-0.04-0.17)	0.689	0.494
AOFAS score	58.40 ± 4.58	58.07 ± 5.41	0.31(-2.32-2.92)	0.237	0.813
Swelling (cm)	1.25 ± 0.20	1.23 ± 0.20	0.15(-0.08-0.11)	0.308	0.759

MD mean difference, CI confidence interval

Compliance with intervention and adverse events

There are no other serious injuries or adverse events related to exercises, and each patient can complete the procedure on time and in accordance with the requirements, with compliance is 100%.

Pain visual analogue scale (VAS) score

There was a significant simple effect between the control group and the intervention group (p < 0.001) after 1d, 3ds, 1 W, 2Ws and 4Ws of the treatment. In the intervention group, the significant simple effect was observed (p < 0.001) with the extension of treatment time. The Bonferroni paired test indicated that pain VAS score showed a decreasing trend (p < 0.001) after 1d, 3ds, 1 W, 2Ws and 4Ws of the treatment, compared to the baseline. The detailed results were displayed in Table 3.

Table 3.

Analysis of the effect of HKE on the VAS of the participants with ankle sprain in two groups

Group	N	Baseline	1st day	3rd day	1st week	2nd week	4th week	F	P	partial η²
Control (Mean ± SD)	29	5.04 ± 0.60	4.64 ± 0.63	3.78 ± 0.51	3.23 ± 0.42	2.42 ± 0.51	0.31 ± 0.25	462.925	< 0.001	0.943
Intervention (Mean ± SD)	30	5.13 ± 0.31	4.02 ± 0.49	3.15 ± 0.48	2.53 ± 0.41	1.57 ± 0.43	0.28 ± 0.23	674.128	< 0.001	0.959
MD(95% CI)		0.09 (-0.04-0.17)	0.62 (0.33–0.92)	0.63 (0.37–0.89)	0.70 (0.49–0.92)	0.85 (0.60–1.09)	0.04 (-0.09-0.16)
t		0.682	4.239	4.859	6.535	6.881	0.601
P		0.499	< 0.001	< 0.001	< 0.001	< 0.001	0.550
Effect Size r		0.09	0.49	0.54	0.65	0.67	0.08
Group main effect								42.151	< 0.001	0.601
Main effect of test times								1040.538	< 0.001	0.974
Group*Test Times								13.305	< 0.001	0.322

NOTE: Bonferroni Multiple Comparison Results. Control: 1st day VS baseline (P < 0.001),3rd day VS baseline (P < 0.001), 1st week VS baseline (P < 0.001), 2nd week VS baseline (P < 0.001), 4th week VS baseline (P < 0.001),3rd day VS 1st day (P < 0.001), 1st week VS 1st day (P < 0.001), 2nd week VS 1st day (P < 0.001), 4th week VS 1st day (P < 0.001), 1st week VS 3rd day (P < 0.001), 2nd week VS 3rd day (P < 0.001), 4th week VS 3rd day (P < 0.001), 2nd week VS 1st week (P < 0.001), 4th week VS 1st week (P = 0.001), 4th week VS 2nd week (P < 0.001). Intervention: 1st day VS baseline (P < 0.001),3rd day VS baseline (P < 0.001), 1st week VS baseline (P < 0.001), 2nd week VS baseline (P < 0.001), 4th week VS baseline (P < 0.001),3rd day VS 1st day (P < 0.001), 1st week VS 1st day (P < 0.001), 2nd week VS 1st day (P < 0.001), 4th week VS 1st day (P < 0.001), 1st week VS 3rd day (P < 0.001), 2nd week VS 3rd day (P < 0.001), 4th week VS 3rd day (P < 0.001), 2nd week VS 1st week (P < 0.001), 4th week VS 1st week (P = 0.001), 4th week VS 2nd week (P < 0.001)

During the treatment period, the pain VAS scores for ankles in two groups decreased gradually at each observation time point (Fig. 3, p < 0.001, p < 0.001) (Baseline, 1st d, 3rd d, 1st W, 2nd W and 4th W). After the treatment for 28 days, we observed that there was no significant difference in the pain VAS scores for ankles between the control group and the intervention group (Fig. 3, p > 0.05). But within-group analysis revealed that the pain VAS scores in the intervention group decreased more rapidly and significantly during the observation period, compared with the control group (Fig. 3, p < 0.001). These above results indicate that both methods can alleviate patient’s ankle pain of the acute lateral ankle sprain, but it has been more effective for HKE, compared with PRICE and ankle bump exercise.

Fig. 3.

Average pain visual analogue scores in control (n = 29), intervention (n = 30) groups at 0 day and after the treatment for 1 day, 3 days,7 days, 14 days, 28 days. the pain VAS scores for ankle in two groups decreased gradually at each observation time point. But the pain VAS scores in the intervention group decreased more rapidly and significantly during the observation period, compared with the control group. Data are presented as means ± SD *p < 0.05,**p < 0.01, *** p < 0.001

Swelling degree

A statistically significant simple effect was found between the control group and the intervention group (p < 0.001) after 1 W, 2Ws and 4Ws of the treatment. But the intervention group showed no significant differences (p > 0.05) after 3 days of the therapies relative to the control group. In the intervention group, a reduction in swelling was observed with prolonged treatment time, but there were no statistically significant differences (p > 0.05) between at 1st week and 3rd day, between at 2nd week and 1st week, between at 4th week and 2nd week (Table 4).

Table 4.

Analysis of the effect of HKE on the edema of the participants with ankle sprain in two groups

Group	N	Baseline	3rd day	1st week	2nd week	4th week	F	P	partial η²
Control (Mean ± SD)	29	1.25 ± 0.20	1.16 ± 0.15	0.92 ± 0.21	0.61 ± 0.19	0.24 ± 0.08	311.681	< 0.001	0.918
Intervention (Mean ± SD)	30	1.23 ± 0.18	1.11 ± 0.14	0.77 ± 0.16	0.32 ± 0.14	0.12 ± 0.06	572.569	< 0.001	0.952
MD(95% CI)		0.02 (-0.08-0.11)	0.05 (-0.02-0.13)	0.16 (0.06–0.25)	0.29 (0.20–0.37)	0.12 (0.08–0.16)
t		0.308	1.360	3.170	6.637	6.534
P		0.759	0.179	0.002	< 0.001	< 0.001
Effect Size r		0.04	0.18	0.39	0.66	0.65
Group main effect							14.156	0.001	0.336
Main effect of test times							714.077	< 0.001	0.962
Group*Test Times							14.450	< 0.001	0.340

NOTE: Bonferroni Multiple Comparison Results. Control: 3rd day VS baseline (P = 0.510), 1st week VS baseline (P < 0.001), 2nd week VS baseline (P < 0.001), 4th week VS baseline (P < 0.001), 1st week VS 3rd day (P = 0.100), 2nd week VS 3rd day (P < 0.001), 4th week VS 3rd day (P < 0.001), 2nd week VS 1st week (P < 0.143), 4th week VS 1st week (P = 0.001), 4th week VS 2nd week (P = 0.160). Intervention: 3rd day VS baseline (P = 0.080), 1st week VS baseline (P < 0.001), 2nd week VS baseline (P < 0.001), 4th week VS baseline (P < 0.001), 1st week VS 3rd day (P = 0.102), 2nd week VS 3rd day (P < 0.001), 4th week VS 3rd day (P < 0.001), 2nd week VS 1st week (P < 0.539), 4th week VS 1st week (P < 0.001), 4th week VS 2nd week (P = 0.114)

After four weeks’ treatment, methods in control and intervention group can both reduce the swelling degree of ankle joint (Fig. 4, p < 0.001, p < 0.001). But the swelling degrees of patients in the intervention group were significantly lower than those in the control group at 1 week, and 2 weeks and 4 weeks after the intervention treatment (Fig. 4, p < 0.05). And then the heel kicking exercise of the intervention group reduced the swelling degree much more effectively and quickly with the extension of the treatment time, compared to the control group.

Fig. 4.

Swelling degrees in control (n = 29), intervention (n = 30) groups at 0 day and after the treatment for 3 days, 7 days, 14 days, 28 days. Swelling degrees for ankle in two groups decreased gradually at each observation time point. But Swelling degrees in the intervention group decreased more rapidly and significantly during the observation period, compared with the control group. Data are presented as means ± SD *p < 0.05,**p < 0.01, *** p < 0.001

AOFAS score

The analysis revealed a significant simple effect for the intervention group (p < 0.001, Table 5) at 1st d, 3rd d, 1st W, 2nd W and 4th W after the treatment, compared to the control group. In the intervention group, the significant simple effect was observed (p < 0.001) as treatment duration increase. Bonferroni paired test indicated that AOFAS score showed an increasing trend (p < 0.001) at 1d, 3ds, 1 W, 2Ws and 4Ws after the treatment, compared to the baseline. The precise results were demonstrated in Table 5.

Table 5.

Analysis of the effect of HKE on the AOFAS scores of the participants with ankle sprain in two groups

Group	N	Baseline	1st day	3rd day	1st week	2nd week	4th week	F	P	partial η²
Control (Mean ± SD)	29	58.38 ± 4.66	68.83 ± 5.12	76.93 ± 3.75	84.55 ± 3.75	89.03 ± 4.53	97.72 ± 1.83	496.591	< 0.001	0.947
Intervention (Mean ± SD)	30	58.07 ± 5.41	78.07 ± 5.05	83.07 ± 5.32	89.17 ± 5.57	93.37 ± 2.93	98.53 ± 1.01	423.722	< 0.001	0.936
MD(95% CI)		0.31 (-2.32-2.92)	-9.22 (-11.89- -6.59)	-6.14 (-8.58- -3.69)	-4.62 (-7.10- -2.13)	-4.33 (-6.34–2.33)	-0.81 (-1.59- -0.30)
t		0.237	6.997	5.008	3.720	4.376	2.113
P		0.813	< 0.001	< 0.001	< 0.001	< 0.001	0.039
Effect Size r		0.03	0.68	0.55	0.44	0.50	0.27
Group main effect								39.185	< 0.001	0.583
Main effect of test times								835.122	< 0.001	0.968
Group*Test Times								15.044	< 0.001	0.350

NOTE: Bonferroni Multiple Comparison Results. Control: 1st day VS baseline (P < 0.001),3rd day VS baseline (P < 0.001), 1st week VS baseline (P < 0.001), 2nd week VS baseline (P < 0.001), 4th week VS baseline (P < 0.001),3rd day VS 1st day (P < 0.001), 1st week VS 1st day (P < 0.001), 2nd week VS 1st day (P < 0.001), 4th week VS 1st day (P < 0.001), 1st week VS 3rd day (P < 0.001), 2nd week VS 3rd day (P < 0.001), 4th week VS 3rd day (P < 0.001), 2nd week VS 1st week (P < 0.001), 4th week VS 1st week (P = 0.001), 4th week VS 2nd week (P < 0.001). Intervention: 1st day VS baseline (P < 0.001),3rd day VS baseline (P < 0.001), 1st week VS baseline (P < 0.001), 2nd week VS baseline (P < 0.001), 4th week VS baseline (P < 0.001),3rd day VS 1st day (P < 0.001), 1st week VS 1st day (P < 0.001), 2nd week VS 1st day (P < 0.001), 4th week VS 1st day (P < 0.001), 1st week VS 3rd day (P < 0.001), 2nd week VS 3rd day (P < 0.001), 4th week VS 3rd day (P < 0.001), 2nd week VS 1st week (P < 0.001), 4th week VS 1st week (P = 0.001), 4th week VS 2nd week (P < 0.001)

As shown in Fig. 5, the scores of the intervention group were significantly higher than those of the control group after one day of treatment. Then with prolonged treatment duration, the scores of both groups gradually increased at observation time point (Fig. 5, p < 0.001, p < 0.001). And there was no significant difference for AOFAS scores between control group and intervention group at the end of the observation (p > 0.05). But AOFAS scores in the intervention group increased more rapidly and significantly during the therapy period, compared with the control group (Fig. 5, p < 0.001). And patients in the intervention group exhibited superior scores relative to the control (Fig. 5, p< 0.001). The above results demonstrate that the earlier heel kicking exercise significantly reduced pain and boosted joint function, which substantially raised the scores.

Fig. 5.

AOFAS scores in control (n = 29), intervention (n = 30) groups at 0 day and after the treatment for 1 day, 3 days,7 days, 14 days, 28 days. AOFAS scores for ankle in two groups decreased gradually at each observation time point. But AOFAS scores in the intervention group decreased more rapidly and significantly during the observation period, compared with the control group. Data are presented as means ± SD *p < 0.05, **p < 0.01, *** p < 0.001

Follow-up

Patients in both groups recorded the Karlsson scores at the 26th week (Control: 100(IQR99-100), Intervention:100(IQR99-100)), with no differences (U = 0.820, P = 0.412).

Discussion

After an ankle sprain, pain and swelling rapidly appear at the injured site, followed by skin ecchymosis. The affected foot becomes immobile due to pain and swelling. When the lateral malleolus is sprained, the pain intensifies when the patient attempts to invert the foot. While rest may alleviate the pain and swelling, ligament laxity can lead to ankle stability, resulting in recurrent sprains [4].

The main findings of the present study were that the treatment of HKE was very much more effective for lowering VAS, alleviating the swelling degrees and increasing AOFAS scores during the treatment period, compared with the control group. But there were no significant differences (VAS score, AOFAS score and Karlsson score) between two groups at the late stage of treatment (the 4th week) and follow-up (the 26th week). Maybe these are associated with the physiological recovery period of the acute lateral ankle sprain (Grade I and II). And it is very effective for HKE to meliorate the symptoms and indexes on the acute lateral ankle sprain.

Some authors also recommend immobilization with a cast or slab in acute ankle sprains [38, 39], whereas some studies have shown that exercise therapy, especially joint stretching, such as achilles sinew stretching exercise [40], can accelerate the recovery of ankle sprain function, range of motion and strength [41, 42]. We also found by within-group analysis that the earlier heel kicking exercise significantly reduced VAS, subsided edema and increased AOFAS scores in intervention group relative to control group at the middle observation time point. The earlier exercise reduced pain and boosted joint function, which substantially raised the scores. We think that the decision to mobilize an ankle sprain has to be individualized based on the extent of soft tissue injury, tenderness, and pain in walking.

Heel kicking exercise (HKE) is an effective active exercise rehabilitation method according to the physiopathology of ankle sprains, combined with the theory of MMBJTP and BSM. When kicking the heel, the ankle joint is stretched and loosened, which contributes to the recovery of the mild malposition of bone. At the same time, HKE may accelerate the blood circulation in the whole body and the skeleton, which leads to reduce the inflammatory response and exudates. In turn, those alleviate the patient’s pain and edema.

It has been unknown whether HKE causes ligaments elongation and joint capsule tears in the intervention group, which could further lead to the instability of the ankle joint. But because HKE is the normal active movement range of the ankle joint which patient can tolerate, it can’t bring about the above bad consequences. In addition, the ankle pump exercise can increase the muscle strength and tension of the soft tissues around the ankle joint, which can prevent ligaments overstretching.

In this study, HKE prior to PRICE and ankle pump treatment was associated with faster pain relief, reduction of edema, and restoration of joint function. More importantly, it has the advantages of simple method, good compliance, less side effects and so on. HKE is a method designed to provide rapid movement rehabilitation for patients with ankle sprains, which can be used as one of its basic treatments. Of course, the number of cases in this study is limited, and further observation is needed to determine whether it can reduce chronic pain and instability in the late stages of ankle sprain. More research is needed to better understand the specific therapeutic potential of HKE as an exercise modality.

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Abbreviations

HKE

Heel kicking exercise

PRICE

Protection, rest, ice, compression pressure bandaging, elevation of the affected limb

BMI

Body mass index

VAS

Visual analogue scale

AOFAS

American orthopedic foot & ankle society ankle-hindfoot scale

TCM

Traditional chinese medicine

BST

Bone setting technique

MMBJTP

Mild malposition of bone and joint, tendon off position

Author contributions

Qin Q-N and Zhang X participated in the design of the study, performed the data analysis, and drafted the manuscript. Qin Q-N, Zhang X, Cai Y-F, Tian T-Z, Zhou J-P, Shi M, Huang P, Li J-H, Liang H-D and Li L performed the assessment and exercise interventions for patients. Wang J-W，Fang Y-X and Tan Z-L collected and analyzed patient data. Li L performed the statistical analyses. Liu B-X and Zheng F were major contributors in the design of this study and revised the manuscript. All the authors read and approved the final manuscript.

Funding

This research received fund from the Major Innovative Technology Project for Collaborative Clinical Practice of Traditional Chinese and Western Medicine in Guangzhou (2023).

Data availability

All data generated or analyzed during this study are presented in the manuscript. Please contact the corresponding author for access to data presented in this study.

Declarations

Ethics approval

This study was approved by the Medical Ethics Committee of TCM hospital affiliated to Guangzhou medical university in China (the Ethics Committee’s ID:2022NK036). All the participants were informed about the purpose, content, and potential risks and benefits of the study and signed an informed consent form. In accordance with the Declaration of Helsinki, all aspects of this study were conducted ethically.

Consent for publication

All participants provided written informed consent for the publication of their anonymized personal and clinical data.

Competing interests

The authors declare no competing interests.