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

Overview

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.

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.