Comparative Effects Of Clamshell And Short Arc Quadriceps Exercises In Patellofemoral Pain (CASCAPE-PFPS)

Comparative Effects Of Clam Shell Exercises And Short Arc Quadriceps Strengthening Exercises On Pain, Functional Disability And Quality Of Life In Patellofemoral Pain Syndrome

This is a research study to compare two different exercises for people who have patellofemoral pain syndrome. Patellofemoral pain syndrome means pain around or behind the kneecap, which is also called "runner's knee".

People in this study will be divided into two groups by chance. One group will do clamshell exercises. This exercise strengthens hip muscles. The other group will do short arc quadriceps exercises. This exercise strengthens thigh muscles near the knee. Both groups will do their exercises for the same number of weeks.

The main goal of this study is to see which exercise reduces knee pain better and helps patients do daily activities more easily. We will also check if quality of life improves after doing these exercises.

Pain level, knee function, and quality of life will be checked before starting exercises and again after finishing the exercise program.

The results may help doctors and physical therapists choose the best exercise for patients with kneecap pain.

Study Overview

• Status: Completed
• Conditions: Patellofemoral Pain Syndrome
• Intervention / Treatment: Procedure: Clamshell Exercise; Procedure: Short Arc Quadriceps Exercise

Detailed Description

This randomized parallel-group clinical trial will compare the effectiveness of clamshell exercises versus short arc quadriceps strengthening exercises in patients diagnosed with patellofemoral pain syndrome.

Study Design: Participants meeting inclusion criteria for patellofemoral pain syndrome will be randomly allocated into two intervention groups.

Group 1 - Clamshell Exercise Group: Participants will perform clamshell exercises targeting hip abductors and external rotators, specifically gluteus medius and gluteus maximus muscles.

Group 2 - Short Arc Quadriceps Group: Participants will perform short arc quadriceps strengthening exercises focusing on quadriceps femoris muscle, with emphasis on vastus medialis obliquus activation.

Intervention Duration: Both groups will follow supervised exercise protocols for [X weeks]. Frequency and repetitions will be as per standard protocol.

Outcome Measures:

Primary: Pain intensity using Visual Analog Scale, Functional disability using Kujala Anterior Knee Pain Scale, Quality of Life using SF-36 questionnaire.

Assessments will be conducted at baseline, mid-intervention, and post-intervention to compare changes between the two exercise groups.

Hypothesis: Clamshell exercises targeting hip muscles may show superior effects on pain and function compared to short arc quadriceps exercises in PFPS patients.

• Study Type: Interventional
• Enrollment (Actual): 34
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Pakistan
  • Punjab Province
    • Sargodha, Punjab Province, Pakistan, 40100
      • Tehsil Headquarter Hospital, Bahlwal

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

Patients diagnosed with Patellofemoral Pain Syndrome Age between 18-40 years. Male and female participants Presence of anterior knee pain for at least 4 weeks Pain aggravated by activities such as stair climbing, squatting, running, or prolonged sitting Willingness to participate and provide informed consent

Exclusion Criteria:

History of knee surgery or fracture around the knee joint Ligament injuries (e.g., ACL, PCL tears) or meniscal injuries Presence of other knee conditions (e.g., osteoarthritis, patellar dislocation). Neurological disorders affecting lower limb sensations and gait Current participation in any other physiotherapy or rehabilitation program Systemic inflammatory conditions (e.g., rheumatoid arthritis). Cognitive impairment or inability to follow instructions/attend sessions. Use of long-term steroids, strong analgesics, or anti-inflammatory medications.

Study Plan

How is the study designed?

Design Details

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

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Clamshell Exercise Group; Participants in this group will perform clamshell exercises targeting hip abductors and external rotators. Exercise includes side-lying hip abduction with knees bent at 45 degrees, focusing on gluteus medius and gluteus maximus strengthening. Sessions will be supervised by physical therapist for [X weeks], [frequency per week].	Procedure: Clamshell Exercise; A hip strengthening exercise performed in side-lying position with hips and knees flexed. Patient opens top knee like a clamshell while keeping feet together to strengthen gluteus medius and external rotators.; Other Names: Sude-lying Hip Abduction; Shell Exercise
Experimental: Short Arc Quadriceps Exercise Group; Participants in this group will perform short arc quadriceps strengthening exercises targeting quadriceps femoris muscle with emphasis on vastus medialis obliquus activation. Exercise performed from 30 to 0 degrees knee extension in short arc range. Sessions will be supervised by physical therapist for [X weeks], [frequency per week].	Procedure: Short Arc Quadriceps Exercise; A knee strengthening exercise performed in short range of motion from 30 degrees to full extension. Patient extends knee against resistance while quadriceps muscle is activated, focusing on vastus medialis obliquus.; Other Names: SAQ Exercise; Terminal Knee Extension; Short Range Quadricepa

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in Pain Intensity	Pain intensity will be assessed using Visual Analog Scale (VAS). VAS is a 10cm horizontal line where 0 = no pain and 10 = worst pain imaginable. Patients mark their current knee pain level. Change in VAS score will be measured from baseline to post-intervention after completion of exercise program.	Baseline and 12 weeks post-intervention

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in Knee Function	Knee function will be assessed using Kujala Anterior Knee Pain Scale (AKPS). AKPS is a 13-item questionnaire specific for patellofemoral pain syndrome. Total score ranges from 0 to 100, where 100 = no limitation and 0 = maximum limitation. Change in AKPS score will be measured from baseline to post-intervention.	Baseline and 12 weeks post-intervention
Change in Quality of Life	Quality of life will be assessed using Short Form-36 Health Survey (SF-36). SF-36 includes 8 domains: physical functioning, role physical, bodily pain, general health, vitality, social functioning, role emotional, mental health. Scores range from 0 to 100 for each domain. Change in SF-36 scores will be measured from baseline to post-intervention.	Baseline and 12 weeks post-intervention

Collaborators and Investigators

• Sponsor: Green International University

Study record dates

Study Major Dates

• Study Start (Actual): November 2, 2025
• Primary Completion (Actual): April 29, 2026
• Study Completion (Actual): May 5, 2026

Study Registration Dates

• First Submitted: June 9, 2026
• First Submitted That Met QC Criteria: June 9, 2026
• First Posted (Actual): June 12, 2026

Study Record Updates

• Last Update Posted (Actual): June 12, 2026
• Last Update Submitted That Met QC Criteria: June 9, 2026
• Last Verified: June 1, 2026

More Information

Terms related to this study

• Keywords: Knee Pain; Physical Therapy; Patellofemoral Pain Syndrome; Quadriceps Strengthening; Clamshell Exercises; Short Arc Quadriceps; Hip Strengthening
• Additional Relevant MeSH Terms: Musculoskeletal Diseases; Joint Diseases; Patellofemoral Pain Syndrome
• Other Study ID Numbers: GIU/REC/26-40

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: Only IPD used in the results publication willbe shared.
• IPD Sharing Time Frame: It will be available after the completion of the study.
• IPD Sharing Access Criteria: Data requests should be sent to the corresponding author. Access will be granted to qualified researchers for approved research proposals. Data will be de-identified before sharing.
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP; ICF; CSR

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No