Brief Summary The goal of this clinical trial is to learn which type of exercise is more effective for reducing knee hyperextension in people who have had a stroke. Knee hyperextension, also called genu recurvatum, occurs when the knee bends too far backward while standing or walking. This problem is common after a stroke and can make walking difficult, reduce balance, increase the risk of falls, and place extra stress on the knee joint. Over time, it may also lead to pain, joint damage, and reduced independence in daily activities.

Stroke is one of the leading causes of long-term disability. Many people who survive a stroke experience weakness, muscle stiffness, balance problems, and difficulty controlling movement on one side of the body. These changes can affect the way a person walks. One common walking problem after stroke is knee hyperextension during the part of walking when the foot is on the ground. This may happen because of muscle weakness, poor balance, reduced body awareness, or difficulty controlling movement. As a result, people may walk more slowly, feel less confident when moving, and have difficulty performing everyday tasks.

Physical therapy plays an important role in helping people recover after a stroke. Exercise programs are commonly used to improve strength, balance, walking ability, and overall function. Two types of exercises frequently used in rehabilitation are Open Kinetic Chain (OKC) exercises and Closed Kinetic Chain (CKC) exercises. However, there is limited research directly comparing these exercise approaches for treating knee hyperextension after stroke.

Open Kinetic Chain exercises involve moving the leg freely while the foot is not fixed to the ground. Examples include straight leg raises, knee extensions while sitting, hip abduction, hip adduction, and hamstring curls. These exercises are often used to strengthen specific muscles and improve movement control.

Closed Kinetic Chain exercises involve movements performed with the foot fixed on the ground or another stable surface. Examples include squats, lunges, step-ups, and side step exercises. These exercises require several joints and muscle groups to work together and may better reflect movements used in everyday activities such as standing, walking, and climbing stairs. They may also improve balance and body awareness.

The main questions this study aims to answer are:

• Does Closed Kinetic Chain exercise reduce knee hyperextension more effectively than Open Kinetic Chain exercise?
• Does Open Kinetic Chain exercise improve knee control and walking ability after stroke?
• Which exercise program leads to greater improvements in muscle strength, balance, mobility, and independence in daily activities?
• Can these exercise programs be safely used as part of stroke rehabilitation? Researchers will compare the effects of these two exercise programs in adults who have experienced a stroke and have weakness on one side of the body. Participants must be able to walk with at least minimal assistance and meet other study requirements. People with certain musculoskeletal conditions, severe communication or cognitive difficulties, or other conditions that may interfere with participation will not be eligible to take part.

A total of 60 participants will be enrolled in the study. Participants will be assigned by chance, similar to flipping a coin, to one of two treatment groups. Thirty participants will receive Closed Kinetic Chain exercises, and thirty participants will receive Open Kinetic Chain exercises. Neither participants nor researchers can choose which group a participant joins. Both groups will continue to receive standard rehabilitation care throughout the study.

Participants will:

• Attend supervised physical therapy sessions three times per week for four weeks.
• Complete a total of 12 treatment sessions.
• Perform exercises designed to improve lower limb strength and movement control.
• Receive either Open Kinetic Chain or Closed Kinetic Chain exercises based on random assignment.
• Continue their routine rehabilitation program alongside the study exercises.
• Complete assessments before starting treatment and again after completing the intervention period.

Participants assigned to the Open Kinetic Chain exercise group may perform activities such as:

• Straight leg raises while lying down.
• Knee extensions while sitting.
• Hip abduction exercises.
• Hip adduction exercises.
• Hamstring curl exercises.

Participants assigned to the Closed Kinetic Chain exercise group may perform activities such as:

• Lunges.
• Semi-squats.
• Forward step-up and step-down exercises.
• Side step-up and step-down exercises.

Researchers will measure several outcomes before and after the treatment period. These measurements will help determine whether either exercise program improves movement and function.

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.

Inclusion Criteria:

• Male and female participants
• Age between 30 and 65 years
• Referred by a neurologist
• Diagnosed case of stroke with one-sided hemiparesis
• Functional ambulatory capacity (Functional Ambulation Category ≥ 2)
• Muscle strength of at least grade 3+ on the Manual Muscle Testing (MMT) scale in the affected lower limb
• No participation in other rehabilitation programs during the study period

Exclusion Criteria:

• Participants with any musculoskeletal condition such as osteoarthritis or ligament laxity
• Significant cognitive, communicative, perceptual, or sensory problems that hinder understanding and/or following verbal commands
• Pregnant individuals