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NCT Number: NCT07646431

Comparative Effects Of Clamshell And Short Arc Quadriceps Exercises In Patellofemoral Pain

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.

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Key information

Age range

18 year–40 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Tehsil Headquarter Hospital, Bahlwal

Sargodha, Punjab Province, 40100, Pakistan

About this study

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.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

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.

Treatment and study plan

Clamshell Exercise

Procedure

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

Short Arc Quadriceps Exercise

Procedure

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

Primary outcomes

  1. Change in Pain Intensity

    Time frame: Baseline and 12 weeks post-intervention

    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.

Secondary outcomes

  1. Change in Knee Function

    Time frame: Baseline and 12 weeks post-intervention

    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.

  2. Change in Quality of Life

    Time frame: Baseline and 12 weeks post-intervention

    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.

Sponsors and collaborators

Lead sponsor

Green International University

Other

Registry information

Official study title

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

Acronym: CASCAPE-PFPS

Important dates

Study start
2025
Primary completion
2026
Study completion
2026
First posted
Jun 12, 2026
Registry last updated
Jun 12, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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