The purpose of this study is to study the effects of core activation on knee joint loading during ambulation in patients with knee osteoarthritis (OA). This study aims to investigate the effects of transversus abdominis (TA) activation during simultaneous kinetic analysis of time to initial peak ground reaction force (T1) at the heel in the sagittal plane.

The objective of this study is to determine whether patients with knee OA demonstrate changes in T1 during comfortable gait speeds when actively contracting the TA muscle. In addition, this study will serve as a pilot study in order to perform a post-hoc power analysis for future study on the effects of the independent variable (TA contraction/changes in core stability) on the dependent variable (T1).

Null hypothesis: There will be no change in T1 in patients with knee OA during gait while contracting their TA.

Alternate hypothesis: There will be a decrease in T1 in patients with knee OA during gait while contracting their TA.

This will be the first study on this topic performed by the investigator. Regarding current knowledge gaps, evidence has shown an influence of core strength measures/stability on lower extremity function. This relationship has been examined very little in patients with knee OA; however, evidence does show a correlation exists. There have been no studies examining the effect of a core strengthening/stability intervention on lower extremity kinetics in patients with knee OA to the PIs knowledge.

This is the first study examining the effects of TA contraction knee loading during gait in this population.

Current evidence shows that core activation/stability may play a role in lower extremity kinetics and kinematics. Most research has focused on younger, more athletic individuals. Research on this population has in the past looked at patellofemoral disorders or ligamentous injury. For example, decreased core function has been shown to increase the risk of sustaining anterior cruciate ligament injury. In addition, increased core stability has resulted in decreased knee loading during athletic activities.

There continues to be an overall paucity of research on proper prescription and dosage of therapeutic exercise for patients with knee OA. Evidence has shown that quadriceps strengthening and aerobic conditioning do lead to decreased disability. Additionally, patients with knee osteoarthritis have decreased postural stability as compared to healthy controls, with a significant correlation being observed between their score on a postural stability measure and the Western Ontario and McMaster Universities Osteoarthritis Index. Patients with knee OA also exhibit decreased overall core stability as compared to healthy controls. This body of research however does not include any evidence on the effects of a core stability intervention on improving overall function.

Knee OA leads to abnormalities in kinetic loading of the lower extremity during ambulation. An increase in T1 in this population has been observed when comparing to healthy controls. Separately, studies have shown that in patients with knee OA, knee joint loading can be influenced by intraarticular hyaluronic acid injections, resulting in decreased T1. Therefore, this study will explore the idea of how activation of a muscle (TA), which plays a large role in core stability, influences kinetic loading (T1) during ambulation in patients with knee OA.

Each participant will only be required to participate for one session, lasting about 1 hour. This does not included the informed consent process requiring approximately 30 minutes of their time prior to participation. Approximately 5 months will be required to enroll all participants. It is the PI's goal to complete primary data analysis no more than 3 months after data collection is complete, so total estimated study time is 8 months.

The primary study endpoint will be the cessation of data collection and the participants' active participation in the research program. The Secondary endpoint will be the completion of data analysis, which concludes the management of PHI.

Primary (exposure to any physical risk) and secondary (management of PHI) safety endpoints are synonymous with the study endpoints mentioned in 8.1.

This project serves as pilot study for future investigation on the role of core stabilization on gait kinetics in patients with knee OA. Therefore the sample size will be small. Post-hoc power analysis will inform the PI about requirements for participant recruitment needs for future investigations.

After informed consent is completed, participants will be scheduled for a session in the Motion Analysis Laboratory in the SAHP. Patients will have already been asked to wear close fitting, exercise appropriate clothing to allow marker placement, and prevent marker blocking during motion analysis. Data collection will begin by collecting the following anthropometric data: body weight (pounds, converted to kilograms) via a scale, height (inches, converted to mm) via a tape measure, leg length from ipsilateral anterior superior iliac spine to ipsilateral medial malleolus bilaterally (cm) via tape measure, and knee and ankle joint widths (cm) via a caliper. After collection of this data is completed and recorded, the PI will place reflective markers on the patient's skin via adhesive tape made for this purpose at the following landmarks bilaterally: ASIS, posterior superior iliac spine, lateral thigh, knee center of rotation, lateral leg, heel, lateral malleolus, and base of the second metatarsal. When this set-up is complete, static calibration of the motion analysis system will take place with the participant standing still in the capture area. When this is complete, the participant will be allowed a 2-minute warm-up by walking back and forth in the capture area. When this is completed the participant will be asked to walk at a comfortable pace across the capture area. Three trials with good force plate contact will be collected. After these three trials are obtained, the patient will lie supine on the mat in the lab, and will be taught how to perform a TA contraction. A Pathway MR-20 biofeedback device (The Prometheus Group, Dover, NH, USA) with two electrodes will be placed just medial to the ASISs on the participant's abdomen. 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 at 50% MVIC. The task will be repeated seated, standing, then ambulating three practice trials on the capture area. The participant will then be instructed to perform an additional three comfortable paced ambulation trials with good force plate contact while contracting the TA enough to cause audible feedback via the biofeedback device. After completing these three trials, the biofeedback device and reflective markers will be removed, and the participant will have completed their active participation in the study.

Inclusion Criteria:

• those with medical diagnosis (providing written evidence from a physician, physician assistant, or nurse practitioner) of knee OA unilaterally or bilaterally.

Exclusion Criteria:

• bilateral total knee arthroplasty, requirement of an assistive device or assistance with ambulation, spinal diagnoses which contraindicate participation in spinal stabilization activities, and those currently limited by another lower extremity pathology at the time of participation.