This will be the second investigation by the PI and sub-investigator on this topic, following the promising results of a pilot study on a small sample size (N=5) completed last year. Whether or not core stabilization influences gait impairments in patients with KOA remains to be seen. Core stabilization has been shown to have positive effects, including increased stride velocity and scores on functional tests like the Functional Reach Test and Timed Up and Go, in older adults. Older adults were also shown to have high compliance with a core stability training program. A systematic review indicated that core training is important to consider when treating older individuals to improve functional use of the extremities, improving participation in activities of daily living, and as part of a fall prevention program. Additionally, it has been shown to benefit young, active individuals in preventing anterior cruciate ligament injury and greater duration of improved outcomes in patients with patellofemoral pain syndrome. Athletes with decreased core control have been shown to be at an increased risk of knee injury as well. One potential cause for this is the ability of the core to improve lower extremity kinematics when activated during challenging single leg weight bearing activity. A recent publication by Azuma, et al. did indicate that paraspinal and anterior abdominal thinning had a negative predictive relationship to the presence of KOA; however, no investigation has explored a cause and effect relationship between core stability/stabilization training and the presence or severity of KOA, nor the gait and functional ability of patients with KOA. This later concept is the focus of this investigation.

Unpublished pilot data collected by the same PI and sub-investigator shows that volitional activation of the TA during self-selected paced ambulation significantly decreases the time to first peak ground reaction force (T1) in the sagittal plane in participants with KOA (D.W. Flowers, C. Frilot, unpublished data, May 2018). This same kinetic gait variable is included in this investigation as one of the dependent variables in all three parts of the investigation.

Nearly four percent of the global population has KOA, with the global female percentage nearing five percent. Additionally, the years lived with disability (YLDs) resulting from the disorder increased by 64.8% from 1990 to 2010. The picture is not much better in the United States, where osteoarthritis ranks eighth highest in YLDs compared to other pathologies. The rate of KOA has continued to climb here in the U.S., doubling in the past half-century even when accounting for increased life expectancy and higher average BMI, both of which are considered risk factors in the development of KOA.

Patients with KOA have been shown to have gait abnormalities when compared to healthy controls, including alterations in trunk and pelvic kinematics, lower extremity kinematics and kinetics, gait speed, and functional outcome measure scores. Some of these differences, like an increased external knee adduction moment (KAM) and a decreased peak stance knee flexion angle (KFA), have been shown to correlate with the advancement of KOA and may be causative in nature. Others, like an increased T1 and reduced freely chosen gait speed, may be compensatory. The same has been found in regard to the reduced second peak ground reaction force in the sagittal plane (F2) observed in this population.

Reduced gait speed alone is predictive of increased fall risk in older adults, without any need to consider additional activities performed during walking tasks. Additionally, the gait impairments observed in this population can be so extreme that they can be more limiting than those observed in patients with diagnoses typically considered more severe, like congestive heart failure, diabetes, heart disease, and stroke. Therefore, improving function via improving gait speed via novel approaches is indicated, but not at the expense of increasing wear and tear on osteoarthritic joints. This investigation aims to show that core stabilization, which has been shown beneficially influence the kinetics and kinematics of lower extremity movements in younger, more active populations, can serve the same purpose in a population with KOA. The investigators are specifically trying to improve self-perceived function and gait speed, via improving the kinetics and kinematics observed in self-selected ambulation.

This investigation will be divided into three parts, each associated with one of the specific aims detailed in Section 1. All procedures will be performed in the School of Allied Health Professions, either in the Motion Analysis Laboratory (Gait Lab) or the Rehabilitation Faculty Practice (RFP) Clinic.

Part 1: Compare age and gender matched healthy controls and KOA groups on kinetics, kinematics, and gait speed during self-selected speed via a between groups analysis across the dependent variables, and determine if those differences in the KOA group have a predictive relationship with their KOOS scores.

Part 2: Within-group comparison of both groups (with and without volitional TA activation) and between-groups (control group versus KOA group). Compare pain levels during both conditions via VAS for the KOA group. Participants will wear biofeedback under both conditions, and all condition trials will be randomized. Alarm or verbal cue will be provided at 30% MVIC, and two electrodes placed over TA/obliquus internus (OI) just medial to anterior superior iliac spine (ASIS). A comparison of TA activation will be performed both within and between groups.

Part 3: Within-groups comparison of KOA group (pre-treatment and post-treatment; six-week training program) on kinetics, kinematics, and gait speed during self-selected paced ambulation. A comparison of KOOS scores before and after treatment with be performed as well.

Once recruitment and informed consent are completed:

Part 1: All participants will undergo anthropometric data collection first, including weight, height, leg length, knee joint width, and ankle joint width. Age matching will be done within +/- 5 years between the two groups. Reflective markers will then be placed on bilateral lower extremities following the Plug in Gait Model. EMG electrodes will be placed bilaterally just medial to the ASIS, over the TA/OI. The Gait Lab will undergo calibration, and the participant will undergo a static trial. In participants with bilateral KOA, the most painful limb, identified by subjective report, will be used in the data collection procedures. Healthy controls will undergo analysis of their dominant limb by indicating with which leg they would kick a ball.

Once the set-up and calibration are completed, the data collection will begin. The participant will be allowed a brief warm-up of 1-2 minutes, walking in the Gait Lab prior to data collection commences. The participant will then be asked to walk at a self-selected pace across the capture area until three trials with good force plate contact are obtained. Good force plate contact is defined as initial contact at the heel and pre-swing/toe off occurring on the force plate, and the absence of any evidence of distraction via the video cameras, such as the participant talking or looking around the lab. These three trials will be used in the kinetic, kinematic, and gait speed data analysis.

See Part 2 for additional trials that will be performed concurrently for both groups. Participants in the experimental group will also be asked to complete a KOOS questionnaire at the same time.

Part 2: Participants will undergo the same procedures described in Part 1 above. While the three trials are obtained for Part 1, three additional walking trials will be concurrently collected for the both groups. These will include the participant volitionally activating their TA during the walking trials, performed and screened exactly the same as in Part 1. These trials will be performed with and without audible biofeedback (via an alarm or verbal cueing), indicating the TA meeting the threshold subsequently discussed below. Investigators will randomly determine whether the trials with or without volitional TA activation are performed first (i.e., Part 1 versus Part 2 trials). The randomization done for Part 2 to determine whether or not the without (Part 1) or with (Part 2) volitional TA activation trials are performed first will be determined via random number generation between 0 and 1 in Excel. Those with 0 will perform the without volitional TA (Part 1) trials first, while those with 1 will perform the with volitional TA activation trials (Part 2) first.

The patient will lie supine on the mat in the lab and will be taught how to perform a TA contraction. Please see the attached script with the instructions that will be used in this education. A baseline maximal contraction will be performed supine, and the amplitude of contraction will be considered maximal voluntary isometric contraction (MVIC). The device will be set to provide audible feedback, or the participant will receive a verbal cue from the investigator, at 30% MVIC. This feedback will be randomized throughout the trials with TA activation via random number generation in Excel, with 0 signifying no cue and 1 indicating a cue. The task will be repeated seated, then standing, prior to data collection.

The experimental group, during both sets of trials, will be asked to subjectively rate their perceived pain in the lower extremity being used in data collection via a 10-point scale, typically used on the VAS, although no visual will be used. Please see the supplemental script document attached to this protocol for the instructions used.

Part 3: Participants in the experimental group will participate in a six-week core stabilization intervention program. Please see the attached intervention program. This program will commence as soon as possible after Parts 1 and 2 of the investigation are completed. Participants will participate in two scheduled intervention sessions each week. Additionally, there will be a home exercise program, consisting of exercises from each week to be performed at home independently. Participants will be provided education and a handout on these exercises by the PI, which will include directions, photographs of the exercises, and a completion check-off for each session. These will be performed three times per week, every other day. The PI will be coordinator of the scheduling and performance of these interventions. These intervention sessions will be performed in the RFP Clinic in the SAHP, either in the open gym or in a private treatment room. This decision will be left up to the participant. More than one participant may or may not undergo intervention with the PI simultaneously, but only with the participants' consent. No more than three participants will undergo the training simultaneously. Training sessions will not be performed on consecutive days in an effort to reduce the chances of delayed onset muscle soreness being present during treatment sessions. Additionally, the core training program includes predetermined guidelines on exercise progressions in order to ensure that the exercises are not progressed too rapidly. The PI will be present and will lead all sessions, ensuring that the exercises and their progressions are done correctly.

After the completion of the intervention program, each participant will undergo gait analysis in the same manner mentioned in Part 1, with the exception of no anthropometric data being collected. Participants will then complete a second, post-intervention KOOS questionnaire, and turn in their home exercise program sheet with tallies from completed sessions. Please see Part 1 for completion of the pre-intervention KOOS questionnaire.

Inclusion Criteria:

• English-speaking men and women
• 40 years old and older
• any race or ethnic group
• a documented diagnosis from a medical provider (i.e., physician, physician assistant, or nurse practitioner, etc.) of KOA, unilaterally or bilaterally.
• Previous or current physical therapy patients may be included (see exclusion criteria for exceptions).

Healthy controls will meet the same requirements, but:

• without a medical diagnosis of KOA
• have the ability to ambulate on a level surface without any report of pain in their knees at the time of gait assessment.

Exclusion Criteria:

• Those with other lower extremity injuries (orthopaedic, cardiovascular, neurologic, etc.) which are currently hindering their ability to ambulate
• those with current complaints of low back pain
• those who have undergone bilateral total knee arthroplasty
• those with concomitant diagnosis of rheumatoid arthritis
• those persons not able to ambulate independently with or without an assistive device
• those who have received a corticosteroid injection within the past two months
• those who have received a hyaluronic acid injection in the past six months
• those persons currently enrolled in a core training program as part of formal physical therapy or physical fitness.

There is not a plan to make IPD available.