The goal of this clinical trial is to learn about how fatigue affects the risk of falling in adults aged 55-70 years with and without knee osteoarthritis. The main questions this trial aims to answer are:

• Does fatigue increase the risk of tripping while walking? and

• Does fatigue increase the risk of falling in response to a trip while walking? Participants will

• Complete questionnaires

• Wear a device that measures physical activity for 5-7 days

• Complete a 30 minute walk on a treadmill

• Complete the following before and after the treadmill walk:

  • Computer test to measure mental fatigue
  • Maximal strength testing
  • Balance test

Researchers will compare adults with and without knee osteoarthritis to see if fall risk in adults with knee osteoarthritis is affected more by walking activity compared to adults without knee osteoarthritis.

Inclusion Criteria:

For adults with knee osteoarthritis:

• presence of occasional to frequent knee pain
• knee pain that is primarily in the medial knee joint compartment
• minimal morning joint stiffness

For all participants:

• able to walk continuously for 30 minutes without an assistive device

Exclusion Criteria:

• fracture or surgery within 1 year
• history of joint replacement
• lower-extremity joint injections within 3 months
• history of stroke or other neurological condition
• cardiovascular or pulmonary conditions that limit daily activity or that preclude participation in exercise
• history of major lower extremity or back injury or pain (except for knee osteoarthritis)
• history of lower extremity amputation
• use an orthotic or prosthetic to walk
• use of beta blockers or other medications that affect fatigue
• use of medications that affect balance
• diabetic neuropathy
• acute illness or the presence of lesions on the torso or lower extremities
• BMI greater than 35
• body weight over 265 lbs