Dynamic Quadriceps Muscle Stimulation for Treatment of Patellofemoral Pain

The purpose of this small, pilot study is to evaluate a novel device that uses neuromuscular electrical stimulation to assist quadriceps muscles as a user walks. This study will involve use of this device on individuals with patellofemoral pain, a relatively common injury among active people, to see if quadriceps stimulation could mitigate disparities in quadriceps activation timing that may indirectly lead to knee pain.

The interventional device will be tested with 20 women aged 18-40 with evidence of patellofemoral pain syndrome (PFPS) and without any co-morbidities that would confound data or contraindications for NMES use. All participants will be enrolled at a single site (Developmental Motor Lab at the University of Texas), and all of a single participant's testing will be complete within a single day with no requirement for follow-up or long-term participation. Participants will have their gait and quadriceps muscle activation patterns evaluated through four six-minute walk tests (6MWT). The first 6MWT will be without a device, second with a device worn but not activated, third with a device activated and stimulating quadriceps musculature, and the fourth without a device. Primary Objective: The purpose of this study is to investigate whether electrical stimulation of the vastus medalis (VM) and/or vastus lateralis (VL) to establish coactivation of these muscles during terminal swing phase impacts severity of PFPS symptoms Secondary Objectives: Secondary purposes for this study include evaluating KneeStim and seeing if there is any evidence of proof of concept in two main areas: KneeStim as a therapeutic device that may assist individuals with joint rehabilitation KneeStim's on-board operating system and motion tracking system as an effective way to monitor joint kinematics. This pilot study has a prospective, controlled, single-center design. Participants and investigators will not be blinded to the treatment. Individuals who evaluate the motion-tracking data between VICON and KneeStim will not be informed which data set aligns with which treatment.

Knee, Pain, Joint, Rehabilitation, Patellofemoral Pain Syndrome, Anterior Knee Pain Syndrome, Knee Pain, Quadriceps

KneeStim is a neuromuscular electrical stimulation (NMES) device that integrates motion-tracking hardware like three-axis accelerometers and a real-time operating system to enable quadriceps muscle stimulation in time with user gait. It is a completely non-invasive device that looks like a light brace and fastens to the user's quadriceps and gastrocnemius muscles. The end goal of this device is to assist with muscle re-strengthening and re-education during a user's everyday activities.

Electromyographic (EMG) readings of vastus lateralis and vastus medialis contraction patterns will be taken after four six-minute walk tests (6MWTs) to evaluate any short-term changes in co-contraction. 6MWT #1: Without interventional device being worn; 6MWT #2: With interventional device being worn, but unpowered; 6MWT #3: With interventional device being worn and operational; 6MWT #4: Without interventional device being worn The time period in which a partipant will be involved is not expected to exceed 90 minutes.

The interventional device uses an on-board operating system that determines stimulation timing and location based on modeled joint kinematics. Movement data will be taken from the device and evaluated against movement data measured by a VICON motion-tracking system during each six-minute walk test to evaluate the accuracy of the device's modeled joint kinematics.

Inclusion Criteria: Aged 18-40 years Symptomatic PFPS on Patella Glide Test, Patella Tilt Test, and Patellar Apprehension Test. Exclusion Criteria: Rheumatoid arthritis or inflammatory arthritis as assessed by licensed physician Use of walking aids other than a cane more than 50% of the time in ambulation Diagnosed knee disorder other than patellofemoral syndrome Pacemaker use, unstable angina, or decompensated heart failure Knee replaced in preceding 12 months or replacement planned within 6 months Moderate to severe dementia Pregnancy (self report) Altered sensation at the knee such that the patient is unable to perceive the presence of pinprick. Use of intra-articular viscosupplementation or steroid injection within preceding 2 months. Use of chronic anticoagulation medication. Movement-limiting pain in the back, hip, ankle, or foot of either lower limb.