Comparison of Open Vs Closed Kinetic Chain Exercises in Genu Recurvatum Among Stroke Patients

Background and Rationale

Stroke remains a leading cause of long-term disability worldwide, ranking among the top causes of death and accounting for a substantial proportion of disability-adjusted life years globally. Post-stroke gait abnormalities are common and vary according to the severity of sensorimotor impairment. One of the most frequently observed deviations in the paretic limb during the stance phase of gait is knee hyperextension, also known as genu recurvatum, which has been reported to affect approximately 40% to 68% of individuals with chronic hemiparetic stroke.

Knee hyperextension compromises joint stability, disrupts normal gait mechanics, and is associated with reduced walking speed and efficiency, as well as pain and an increased risk of long-term musculoskeletal complications such as joint degeneration. The condition is thought to arise from a combination of factors, including quadriceps weakness, plantar flexor spasticity, weak gluteal and hamstring muscles, limited ankle dorsiflexion, hip flexion contracture, and proprioceptive deficits. Because the underlying causes vary across individuals, rehabilitation strategies that fail to address the specific contributing impairments may be less effective.

Several intervention approaches have been described for managing post-stroke knee hyperextension, including functional electrical stimulation, electrogoniometric biofeedback, orthotic management, and surgical intervention; however, no consistently established best-practice rehabilitation protocol currently exists. Progressive resistance training (PRT) is widely used in stroke rehabilitation to increase muscle strength and improve functional outcomes, and is broadly categorized into open kinetic chain (OKC) and closed kinetic chain (CKC) exercise approaches.

OKC exercises involve movement of the distal limb segment in a non-weight-bearing position (for example, seated knee extension or straight leg raise) and are typically used to isolate and strengthen specific muscle groups, though they provide comparatively less joint stability and proprioceptive input. CKC exercises involve movement with the distal segment fixed against a surface in a weight-bearing position (for example, squats, step-ups, or lunges); these exercises are considered more functional, as they more closely replicate movement patterns used in walking and other activities of daily living, and are thought to enhance proprioception, joint stability, and coordinated multi-joint muscle activation.

While prior research has examined OKC and CKC exercises individually, or as components of broader lower-limb strengthening programs following stroke, direct comparative evidence regarding their relative effectiveness specifically for managing knee hyperextension remains limited. This study is designed to address that gap by directly comparing the effects of OKC and CKC exercise programs on knee hyperextension, joint stability, gait, functional mobility, and balance in individuals with chronic post-stroke hemiparesis.

Objectives

The primary objective is to compare the effects of open kinetic chain and closed kinetic chain exercises on knee hyperextension (genu recurvatum) in individuals with post-stroke hemiparesis. Secondary objectives are to determine which exercise approach is more effective in improving knee joint stability, muscle strength, gait and functional mobility, performance of activities of daily living, and dynamic balance.

Hypotheses

Null hypothesis (H0): There is no statistically significant difference between the effects of closed kinetic chain exercises and open kinetic chain exercises on knee hyperextension in stroke patients.

Alternative hypothesis (Ha): There is a statistically significant difference between the effects of closed kinetic chain exercises and open kinetic chain exercises on knee hyperextension in stroke patients.

Study Design and Setting This is a single-blind, randomized controlled trial. Participants will be recruited from the Physiotherapy Outpatient Department of Dow Ojha Hospital, the Department of Institute of Physical Medicine and Rehabilitation (DIPMR), Dow University of Health Sciences, and Health Icon, Karachi, Pakistan, following approval from the Institutional Review Board of Dow University of Health Sciences.

Population and Eligibility

A total of 60 participants will be enrolled and randomly allocated, using a computer-generated randomization sequence, into two equal groups of 30 participants each: Group A (closed kinetic chain exercise group) and Group B (open kinetic chain exercise group). The required sample size was calculated using OpenEpi statistical software, based on post-intervention means and standard deviations reported in prior literature (Group A: 78 ± 12.57; Group B: 87.44 ± 11.69), to achieve 95% power at a significance level (alpha) of 0.05.

Inclusion criteria: men and women aged between 30 and 65 years; referred by a neurologist with a diagnosed case of stroke and one-sided hemiparesis; minimal ambulatory capacity (Functional Ambulation Category ≥ 2); muscle strength of at least grade 3+ on Manual Muscle Testing in the affected lower limb; and no concurrent participation in any other rehabilitation program during the study period.

Exclusion criteria: presence of any musculoskeletal condition such as osteoarthritis or ligamentous laxity affecting the lower limb; significant cognitive, communicative, perceptual, or sensory impairment limiting the ability to understand or follow verbal instructions; and pregnancy.

Randomization and Blinding

Eligible participants will be screened and, upon meeting inclusion criteria, will provide written informed consent (available in English and Urdu) after the purpose, procedures, risks, and potential benefits of the study have been explained. Each participant will then be randomly assigned to Group A or Group B using a computer-generated randomization sheet. To reduce assessment bias, the outcome assessor will be blinded to each participant's group allocation; both groups will continue to receive standard physiotherapy care alongside their assigned study intervention.

Interventions

Group A (Closed Kinetic Chain Exercises): lunges; semi-squats; forward step-up and step-down; side step-up and step-down.

Group B (Open Kinetic Chain Exercises): straight leg raises in lying position; knee extension in sitting position; hip abduction in lying position; hip adduction in lying position; prone hamstring curls.

Both groups will begin with 10 repetitions per set, one set per exercise, performed three sessions per week for 4 weeks (12 sessions total), with each session lasting approximately 30 minutes. Progression will be individualized: participants who consistently report low discomfort (below 3 on the Visual Analogue Scale) will be progressed by increasing the number of sets, while repetitions per set remain constant.

Outcome Measures Primary outcome measures are knee hyperextension angle, assessed using a standard goniometer, and lower-limb muscle strength, assessed using an isokinetic dynamometer, regarded as the gold-standard tool for muscle strength testing and capable of evaluating both concentric and eccentric contraction.

Secondary outcome measures include gait and functional mobility (Dynamic Gait Index), activities of daily living (Barthel Index), and dynamic balance (Berg Balance Scale), a validated tool widely used in stroke rehabilitation research. All outcome measures will be recorded at baseline and again following completion of the 4-week intervention period.

Statistical Analysis

Data will be analyzed using SPSS version 27. Means and standard deviations will be computed for continuous variables such as age, while frequencies and percentages will be reported for categorical variables. Repeated-measures ANOVA will be used to evaluate within-group changes over time and between-group differences across all outcome measures. Independent variables include age and gender; dependent variables include knee hyperextension, functional mobility, activities of daily living, muscle strength, and balance. A p-value of less than 0.05 will be considered statistically significant.

Significance and Expected Outcomes

There is currently no consistently established best-practice exercise approach for managing knee hyperextension after stroke, and existing literature has rarely compared OKC and CKC exercises directly for this specific impairment. By generating direct comparative evidence, this trial is expected to help clinicians select more targeted, evidence-based exercise interventions, potentially improving knee joint stability, gait mechanics, balance, and independence in activities of daily living for stroke survivors, while reducing the risk of secondary musculoskeletal complications.

Anticipated Limitations

Anticipated limitations include possible participant dropout, whether voluntary or involuntary, and potential confounding effects from concurrent medication use among participants.

• Barthel Index (BI) [Срок оценки: The Barthel Index will be assessed at baseline and after 4 weeks of intervention to measure changes in activities of daily living and functional independence]
• Gait Dynamic Index [Срок оценки: The Dynamic Gait Index takes approximately 10-15 minutes to administer and can be assessed at baseline and after the intervention period (4 weeks) to evaluate changes in dynamic balance and gait performance.]
• Berg Balance Scale [Срок оценки: he Berg Balance Scale takes approximately 15-20 minutes to administer and can be assessed at baseline and after the intervention period (4 weeks) to evaluate changes in balance performance]