Every runner dreads the topic and cringes at the question: does running increase your risk of developing arthritis?  Until recently the accepted assumption was yes.  While runners do develop a multitude of overuse injuries related to logging mile after mile on the roads and trails, recent research has confirmed that runners are actually less likely to develop knee osteoarthritis.

Understanding Osteoarthritis
Osteoarthritis occurs as articular joint cartilage which protects the joint becomes rough, cracked, or pitted.  Wear of articular cartilage leaves the hyper-sensitive outer layer of bone (periosteum) exposed, resulting in joint pain and stiffness.  Trauma is the main cause of osteoarthritis.  The major joints associated with running (knees, hips, ankles, lumbar spine) are more susceptible to osteoarthritis with the addition of increased torsional force.  The main cause of abnormal torsion associated with running through a joint is muscular weakness.

What Healthy Joints Need
In order to minimize joint wear which can lead to osteoarthritis, joints need movement.  While excessive force and torsion through a joint can be detrimental, lack of motion as occurs in a sedentary lifestyle, can be just as harmful to joint health.  Loading and unloading a joint as the joint moves through its range of motion allows the joint to be “self-lubricated” by synovial fluid. Running with efficient technique in the absence of past trauma or arthritis is an excellent way to insure joint health.  Prolonged sitting or standing, however, is detrimental to joint articular cartilage health.

Recent Research Explained
The July 2013 study published in Medicine & Science in Sports & Exercise compared loads through the knee joint in separate samples of walkers and runners.  Runners typically place loads of eight times their body weight through the knee joint, while walkers place two to three times their body weight through the knee joint.  The key difference, however, lies in the duration and frequency of knee joint loading in runners versus walkers.  Running, the study concluded, loads the knee joint for a shorter period of time.  In addition, due to the increased speed of running compared to walking, fewer impact moments are experienced when running.  The overall impact of running versus walking was concluded to be the same over a given distance.  Walking has long been the exercise of choice for joint health.  The research cited has shown that running may be at least as beneficial to health as walking.

Factors Not To Ignore
Body Mass Index (BMI) is a widely accepted calculation to determine if a person is underweight, within healthy limits, or overweight.  Among the health risks associated with being overweight are diabetes, heart disease, cancer, and osteoarthritis.  Underweight individuals have an increased risk of osteopenia and osteoporosis which increased fracture risk associated with falling.  Aerobic exercise such as running generally reduces one’s BMI resulting in overall health and reduced joint forces with each stride.  But BMI does not consider a huge component of health which is fitness.  Body fat percentage is not factored into BMI.  The fact that muscle is more dense and heavier than body fat often skews BMI calculations.  Similarly, extremity and core muscle strength is not factored into BMI calculations.  The greatest way to decrease joint osteoarthritis and running related overuse injuries is through excellent extremity and core strength.  Without adequate extremity and core strength, the joints associated with running are vulnerable to compression and torsion.
Body Mass Index Scale
• BMI of less than 18 means you are under weight.
• BMI of less than 18.5 indicates you are thin for your height.
• BMI between 18.6 and 24.9 indicates you are at a healthy weight.
• BMI between 25 and 29.9 suggests you are overweight for your height.
• BMI of 30 or greater indicates obesity. If you are obese, consider consulting a doctor or losing weight.

Finally, past joint injury, past joint surgical intervention both predispose an individual to osteoarthritis even with the recent favorable research.  Talk to a physical therapist or your physician to determine how your past medical history may influence your ability to run pain-free.  A smart, progressive training program coupled with a solid extremity and core conditioning program will maximize your ability to run for years to come.

John Fiore, PT
Sapphire Physical Therapy