Effects of Clamshell Exercises in Addition to Standardized Physical Therapy in the Management of Patellofemoral Pain Syndrome

July 23, 2026 updated by: Ibadat International University, Islamabad

Effects of Clamshell Exercises in Addition to Standardized Physical Therapy in the Management of Patellofemoral Pain Syndrome. A Randomized Controlled Trial

This randomized controlled trial aims to evaluate whether adding clamshell exercises to standardized physical therapy provides greater improvements in pain and knee function than standardized physical therapy alone in individuals with patellofemoral pain syndrome (PFPS). PFPS is a common musculoskeletal condition characterized by pain around or behind the kneecap that is aggravated by activities such as stair climbing, squatting, running, and prolonged sitting.

Participants aged 18-45 years with clinically diagnosed PFPS will be randomly assigned to one of two groups. The control group will receive standardized physical therapy consisting of warm-up exercises, stretching, quadriceps and lower-limb strengthening exercises, and cool-down activities. The experimental group will receive the same standardized physical therapy program with the addition of clamshell exercises targeting the gluteus medius and hip external rotator muscles.

Both groups will participate in supervised treatment sessions lasting approximately 45 minutes, three times per week, for four weeks. Pain intensity will be measured using the Numeric Pain Rating Scale (NPRS), and knee function will be assessed using the Kujala Anterior Knee Pain Scale before and after the intervention. The findings of this study may help determine whether incorporating clamshell exercises into routine physiotherapy improves rehabilitation outcomes for patients with PFPS.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Completed

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Detailed Description

Patellofemoral pain syndrome (PFPS) is one of the most common causes of anterior knee pain, affecting both physically active individuals and the general population. The condition is associated with pain during activities that increase patellofemoral joint loading, including squatting, stair climbing, running, jumping, and prolonged sitting. Altered lower-limb biomechanics, particularly weakness of the hip abductors and external rotators, may contribute to excessive femoral internal rotation and dynamic knee valgus, thereby increasing patellofemoral joint stress.

Conventional physiotherapy for PFPS typically includes stretching, quadriceps strengthening, and functional rehabilitation. Although these interventions are beneficial, many patients continue to experience persistent symptoms or recurrence. Recent evidence suggests that strengthening the hip musculature, particularly the gluteus medius, may improve lower-limb alignment and reduce patellofemoral joint stress. The clamshell exercise is a simple, low-cost exercise designed to activate the hip abductors and external rotators and may provide additional clinical benefit when combined with standard physiotherapy.

The purpose of this randomized controlled trial is to determine whether adding clamshell exercises to standardized physical therapy results in greater reductions in pain and improvements in knee function compared with standardized physical therapy alone in patients with PFPS.

Participants aged 18-45 years who meet the American Physical Therapy Association clinical diagnostic criteria for PFPS and have symptoms lasting at least three months with a pain score of 3 or higher on the Numeric Pain Rating Scale (NPRS) will be recruited. Participants with previous knee surgery, significant ligament or meniscal injuries, patellar dislocation, osteoarthritis, lumbar radiculopathy, hip pathology, systemic inflammatory arthritis, recent corticosteroid injection or surgery, neuromuscular disorders, pregnancy, or other exclusion criteria will not be eligible.

Approximately 40 participants will be enrolled using purposive sampling after accounting for potential loss to follow-up. Participants will be randomly allocated into one of two treatment groups:

Control Group: Standardized physical therapy. Experimental Group: Standardized physical therapy plus clamshell exercises.

Both groups will receive equal treatment duration of approximately 45 minutes per session, three sessions per week for four weeks. Standardized physical therapy includes warm-up activities, stretching of the hamstrings, quadriceps, gastrocnemius-soleus complex, and iliotibial band, quadriceps and lower-limb strengthening exercises, and cool-down stretching. The experimental group will additionally perform side-lying clamshell exercises (3 sets of 12-15 repetitions) during each treatment session.

Outcome assessments will be performed at baseline and after completion of the intervention. Pain intensity will be evaluated using the Numeric Pain Rating Scale (NPRS), while knee function will be assessed using the Kujala Anterior Knee Pain Scale. Statistical analyses will be conducted using SPSS version 27. Appropriate parametric or non-parametric tests will be selected based on data distribution, with statistical significance established at p < 0.05.

Ethical approval will be obtained from the Research Ethics Review Committee of Ibadat International University, Islamabad, and permission will be obtained from Alkhidmat Hospital, Peshawar. Written informed consent will be obtained from all participants before enrollment. Participant confidentiality will be maintained throughout the study, and participation will be voluntary with the right to withdraw at any stage without penalty.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Actual)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
40

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Pakistan
    • KPK
      • Charsadda, KPK, Pakistan, 24420
        • Tahir general Hospital Charsadda

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

  • Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Adults aged 18 to 45 years. Male or female participants. Clinically diagnosed with patellofemoral pain syndrome (PFPS) according to the American Physical Therapy Association (APTA) clinical practice guidelines.

Presence of retropatellar or peripatellar pain. Reproduction of retropatellar or peripatellar pain during squatting or other functional activities that load the patellofemoral joint in knee flexion.

Symptoms present for at least 3 months. Pain intensity of ≥3 on the Numeric Pain Rating Scale (NPRS) during aggravating activities.

Able and willing to provide written informed consent and comply with the study procedures.

Exclusion Criteria:

  • History of knee surgery, ligament injury, meniscal tear, patellar dislocation, or knee osteoarthritis.

Lumbar radiculopathy, hip pathology, or systemic inflammatory arthritis (e.g., rheumatoid arthritis).

Corticosteroid injection or knee surgery within the previous 3 months. Neuromuscular disorders affecting muscle function (e.g., stroke or Parkinson's disease).

Pregnancy or within 6 months postpartum. Family history of early degenerative joint disease. Any condition that, in the investigator's opinion, would interfere with safe participation or completion of the study.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Single

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: Standardized Physical Therapy (Control)
Participants will receive standardized physical therapy consisting of warm-up exercises, stretching, quadriceps and lower-limb strengthening exercises, and cool-down activities. Each treatment session will last approximately 35 minutes, three times per week for four weeks.
Behavioral: Standardized Physical Therapy
Standardized physical therapy consists of warm-up exercises, stretching of the hamstrings, quadriceps, gastrocnemius-soleus, and iliotibial band, quadriceps and lower-limb strengthening exercises (including static quadriceps exercises, straight leg raises, hip strengthening exercises, and mini-squats), followed by cool-down stretching. The control group receives this intervention for approximately 35 minutes per session, three sessions per week for four weeks.
Other Names:
  • Conventional Physiotherapy
Experimental: Standardized Physical Therapy + Clamshell Exercises
Participants will receive standardized physical therapy together with side-lying clamshell exercises targeting the gluteus medius and hip external rotator muscles. Treatment sessions will last approximately 45 minutes, three times per week for four weeks. The only additional intervention compared with the control group is the inclusion of clamshell exercises.
Behavioral: Standardized Physical Therapy with Clamshell Exercise
Participants perform side-lying clamshell exercises to strengthen the gluteus medius and hip external rotator muscles. The exercise is performed as 3 sets of 12-15 repetitions under physiotherapist supervision. This intervention is added to standardized physical therapy in the experimental group, resulting in a total treatment time of approximately 45 minutes per session, three sessions per week for four weeks.
Other Names:
  • Side-lying Clamshell Exercise

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
Change in Pain Intensity Measured by the Numeric Pain Rating Scale (NPRS)
Time Frame: Baseline and Week 4 (end of intervention)
Pain intensity will be assessed using the 11-point Numeric Pain Rating Scale (NPRS), where 0 indicates no pain and 10 indicates the worst imaginable pain. The primary outcome is the change in NPRS score from baseline to the end of the intervention.
Baseline and Week 4 (end of intervention)

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Change in Knee Function Measured by the Kujala Anterior Knee Pain Scale
Time Frame: Baseline and Week 4 (end of intervention)
Knee function will be evaluated using the Kujala Anterior Knee Pain Scale, a validated patient-reported outcome measure assessing symptoms and functional limitations associated with patellofemoral pain syndrome. The secondary outcome is the change in Kujala score from baseline to the end of the intervention.
Baseline and Week 4 (end of intervention)

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Ibadat International University, Islamabad

Investigators

Investigators

A researcher involved in a clinical study. Related terms include site principal investigator, site sub-investigator, study chair, study director, and study principal investigator.
  • Principal Investigator: Dr Muhammad Nazim Farooq Dean, Phd, Ibadat International University, Islamabad

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

  • Neal BS, Lack SD, Lankhorst NE, Raye A, Morrissey D, van Middelkoop M. Risk factors for patellofemoral pain: a systematic review and meta-analysis. Br J Sports Med. 2019;53(5):270-81. 2. Lack S, Barton C, Sohan O, Crossley K, Morrissey D. Proximal muscle rehabilitation is effective for patellofemoral pain: a systematic review with meta-analysis. Br J Sports Med.2015;49(21):1365-76. 3. Rathleff MS, Roos EM, Olesen JL, Rasmussen S. Exercise during school hours when added to patient education improves outcome for 2 years in adolescent patellofemoral pain: a cluster randomised trial. Br J Sports Med. 2015;49(6):406-12. 4. Bolgla LA, Boling MC. An update for the conservative management of patellofemoral pain syndrome: a systematic review of the literature from 2000 to 2010. Int J Sports Phys Ther. 2011;6(2):112-25. 5. Powers CM. The influence of abnormal hip mechanics on knee injury: a biomechanical perspective. J Orthop Sports Phys Ther. 2010;40(2):42-51. 6. Ferber R, Bolgla L, Earl-Boehm JE, Emery C, Hamstra-Wright K. Strengthening of the hip and core versus knee muscles for the treatment of patellofemoral pain: a multicenter randomized controlled trial. J Athl Train. 2015;50(4):366-77. 7. Khayambashi K, Fallah A, Movahedi A, Bagwell J, Powers C. Posterolateral hip muscle strengthening versus quadriceps strengthening for patellofemoral pain: a comparative control trial. Arch Phys Med Rehabil. 2014;95(5):900-7. 8. Santos TR, Oliveira BA, Ocarino JM, Holt KG, Fonseca ST. Effectiveness of hip muscle strengthening in patellofemoral pain syndrome patients: a systematic review. Braz J Phys Ther. 2015;19(3):167-76. 9. Kamel AM, Ghuiba K, Abd Allah DS, Fayaz NA, Abdelkader NA. Effect of adding short foot exercise to hip and knee focused exercises in treatment of patients with patellofemoral pain syndrome: a randomized controlled trial. J Orthop Surg Res. 2024;19(1):207. 10. Alammari A, Spence N, Narayan A, Karnad SD, Ottayil ZC. Effect of hip abductors and lateral rotators' mu

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
January 10, 2026

Primary Completion (Actual)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
May 30, 2026

Study Completion (Actual)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
June 10, 2026

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
July 23, 2026

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
July 23, 2026

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
July 28, 2026

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
July 28, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
July 23, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
July 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • IIUI/RERC/ADT/2026/O2/229

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

Individual participant data (IPD) collected during this study will not be made publicly available because informed consent for public data sharing was not obtained, and sharing could compromise participant confidentiality. Aggregate study results will be reported in publications and presentations without identifying individual participants.

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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