An interventional study of Isometric VMO Exercise and Isotonic VMO Exercise in Patellofemoral Pain Syndrome and Anterior Knee Pain, sponsored by Firat University. Recruiting at 1 site in Turkey (Türkiye). Open to participants aged 18 Years to 50 Years. Per ClinicalTrials.gov, last updated 2026-08-11.
Sponsored by Firat University · Not applicable, Interventional, and Treatment
Patellofemoral pain syndrome (PFPS) is a common musculoskeletal condition characterized by anterior knee pain, especially during activities such as stair climbing, squatting, running, and prolonged sitting. Weakness or delayed activation of the vastus medialis oblique (VMO) muscle is considered an important contributing factor in the development of PFPS.
This study aims to compare the effects of three different types of VMO strengthening exercises (isometric, isotonic, and eccentric) applied within the terminal knee extension range (0-30°) on pain, functional performance, and muscle architecture in individuals with PFPS.
Participants will be randomly assigned to one of three exercise groups. All participants will receive a standardized physiotherapy program, including heat therapy, TENS, and therapeutic ultrasound, followed by group-specific VMO strengthening exercises. The intervention will be performed three times per week for 8 weeks.
Outcomes will be assessed before and after the intervention and will include pain intensity (Visual Analog Scale), functional performance (WOMAC, 30-second sit-to-stand test, and stair test), and muscle architecture parameters measured by ultrasound imaging.
The results of this study are expected to provide evidence for optimizing rehabilitation strategies in individuals with PFPS.
Patellofemoral pain syndrome (PFPS) is a prevalent condition affecting physically active individuals and is associated with anterior knee pain during functional activities. Alterations in patellofemoral joint biomechanics, particularly related to quadriceps muscle imbalance and insufficient activation of the vastus medialis oblique (VMO), are considered key contributing factors.
Although VMO strengthening is widely used in clinical practice, there is limited evidence comparing the effects of different contraction types-specifically isometric, isotonic, and eccentric exercises-applied within the terminal knee extension range (0-30°), where patellofemoral joint stress and stabilization demands are highest.
This study is designed as a three-arm, parallel-group, randomized controlled trial to investigate the comparative effects of these exercise modalities on pain, functional outcomes, and muscle architecture. The intervention period will last 8 weeks, with sessions conducted three times per week.
A total of 90 participants aged 18-40 years with clinically diagnosed PFPS will be recruited and randomly allocated into three groups: isometric, isotonic, and eccentric exercise groups. All participants will receive a standardized physiotherapy protocol including superficial heat application, transcutaneous electrical nerve stimulation (TENS), and therapeutic ultrasound prior to exercise.
Primary outcomes will include pain intensity assessed by the Visual Analog Scale (VAS) and functional status evaluated using the WOMAC index, 30-second sit-to-stand test, and stair ascent/descent test. Secondary outcomes will include ultrasonographic assessment of muscle architecture, including muscle thickness, fascicle length, pennation angle, and physiological cross-sectional area of the VMO muscle. Additionally, selected hip muscles (adductor group and tensor fascia lata) will be evaluated.
Assessments will be performed at baseline (T0) and after the 8-week intervention (T1) by a blinded assessor. Randomization will be conducted using a computer-generated sequence with allocation concealment.
Statistical analyses will include repeated measures analysis to evaluate within-group and between-group differences, with significance set at p \< 0.05.
The findings of this study are expected to contribute to evidence-based rehabilitation by identifying the most effective type of VMO strengthening exercise for improving clinical outcomes and muscle structure in individuals with PFPS.
297 studies on the registry are indexed under Patellofemoral Pain Syndrome; 74 are open to participants now.
This study's planned enrollment of 90 is above the median of 45 across 244 interventional studies indexed under Patellofemoral Pain Syndrome.
Browse Patellofemoral Pain Syndrome studies →Firat University is the lead sponsor of 117 studies on the registry; 46 are open to participants now.
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Exclusion Criteria:
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You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Participants in this group will receive a standardized physiotherapy program (hot pack, TENS, and therapeutic ultrasound) followed by isometric VMO strengthening exercises performed in the terminal knee extension range (0-30°). Exercises will be performed 3 sets of 10 repetitions, with 10-second contractions, three times per week for 8 weeks.
Other: Isometric VMO Exercise
Participants will receive the same standardized physiotherapy program followed by isotonic (concentric and eccentric) VMO strengthening exercises performed within the 0-30° knee extension range using external resistance. Exercises will be performed 3 sets of 10-15 repetitions, three times per week for 8 weeks.
Other: Isotonic VMO Exercise
Participants will receive the same standardized physiotherapy program followed by eccentric VMO strengthening exercises performed within the 0-30° knee extension range. Exercises will be performed 3 sets of 10-15 repetitions, three times per week for 8 weeks.
Other: Eccentric VMO Exercise
Isometric contractions of the vastus medialis oblique muscle will be performed with the knee supported at approximately 15° flexion, emphasizing maximal voluntary contraction without joint movement.
Also known as: Experimental: Isometric Exercise Group
Participants will perform controlled concentric and eccentric contractions using ankle weights through a limited range of motion (0-30° knee extension).
Participants will perform eccentric contractions against resistance during knee flexion, with assisted concentric return to the starting position.
VMO Muscle Architecture (Ultrasound)
Muscle thickness, fascicle length, pennation angle, and physiological cross-sectional area of the vastus medialis oblique muscle will be assessed using ultrasound imaging.
Time frame: Baseline and Week 8
Pain Intensity (Visual Analog Scale, VAS)
Pain intensity will be assessed using the Visual Analog Scale (VAS), a 10-cm scale ranging from 0 (no pain) to 10 (worst imaginable pain). Higher scores indicate greater pain intensity.
Time frame: Baseline and Week 8
Functional Status (WOMAC Index)
Functional status will be evaluated using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), including pain, stiffness, and physical function subscales. Higher scores indicate worse functional status.
Time frame: Baseline and Week 8
30-Second Sit-to-Stand Test
The number of repetitions completed in 30 seconds will be recorded to assess lower extremity functional strength.
Time frame: Baseline and Week 8
Stair Ascent and Descent Test
Time required to ascend and descend a standardized 9-step staircase will be recorded in seconds.
Time frame: Baseline and Week 8
Hip Muscle Architecture (Ultrasound)
Muscle architecture parameters of the hip muscles (adductors and tensor fascia lata) will be evaluated using ultrasound imaging.
Time frame: Baseline and Week 8
Plan to share: No
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