It What is Osteoarthritis (OA)?

Osteoarthritis (OA) is a condition where cartilage on the end of bones begins to break down. Because cartilage acts as a cushion between bones, its job is to provide a smooth surface for joint motion. As cartilage deteriorates, the space between the two bones becomes smaller and less smooth. This can lead to joint stiffness and/or pain.

Image 1 shows the progression of OA in the knee.  OA typically occurs in larger weight-bearing joints (ie: the knee and hip), but can occur in any joint.

knee pain

Unfortunately, many people believe that joint degeneration is a part of “getting old.” However, it is not normal to have consistent pain no matter how old you are.

Living with OA can place serious limitations on a person’s lifestyle. For example, people with knee osteoarthritis have trouble with many activities of daily living, like getting dressed, walking, and sleeping.

Some over the counter drugs may help with symptoms of pain and stiffness, but they do not cure arthritis. Currently, there is no cure for OA. However, there are many ways to prevent OA and manage your symptoms.

Risk Factors

There are a number of risk factors for OA.  Some are in our control (modifiable) and some are not (non-modifiable). The non-modifiable risk factors, such as age and history of developmental hip disorders cannot be altered by changes in behavior.

Body Mass Index

Fortunately, a major modifiable risk factor  is body mass index (BMI).1 BMI is a ratio of weight to height (in kg/m2).  It is most commonly used to classify a person’s health status. The higher the ratio, the greater a person’s risk of developing health conditions like heart disease, diabetes, and OA. See Figure 1 below for BMI norms.

weight loss Chicago

Relating Weight to OA

Society has been promoting weight loss since the beginning of time. Let’s consider some of the theories that help explain why increased weight may cause joint pain and degeneration:

Theory #1: The Mechanical and Structural Hypothesis

First, when a person has more mass, more load is placed on their joints during movement. This increased load over time can lead to joint degeneration. For example, studies have shown that the joint space in the knee is smaller in people who are obese.2 This reduced joint space disrupts the congruency of the joint surfaces. As a result, people will experience movement limitations and feelings of stiffness.

Someone who is classified as obese will use less efficient strategies for balance and walking to compensate for the additional joint load. Ultimately, these compensations may contribute to joint break down.

Theory #2: Chemical Mediators

Second is the presence of chemical mediators. Unfortunately, fat cells do not just statically sit under our skin. They are constantly releasing chemicals like inflammatory cytokines and leptin. Researchers propose that release of inflammatory cytokines cause the body to experience more intense pain.

Similarly, leptin has been found in the synovial fluid (joint fluid) of patients with OA and may be related to both inflammation and joint damage.

Theories #3-6: Depression, Sleep, and Lifestyle

Thirdly, people who experience depression, sleep deprivation, and live a sedentary lifestyle tend to have altered perceptions of pain and therefore, an increased risk of developing OA. In some way, all of these factors contribute to inactivity and/or weight gain.

Please note that none of these hypotheses are correct on their own. There are many factors outside the scope of this article that are involved in the relationship between weight and OA. However, it is important to recognize that increased weight may contribute to joint problems. The good news is weight loss can be achieved with appropriate lifestyle changes.

Osteoarthritis and Exercise: Does Exercise Really Make a Difference?

In short, YES. One study found that dieting alone was not sufficient to reduce symptoms in people with OA. Exercise combined with a healthy eating plan resulted in more significant changes. Similarly, research has shown that weight reduction significantly affects both cartilage thickness and integrity. The participants in this study who saw the greatest changes were those who lost more than 10% of their body weight over 4 years. This group also reported less pain, stiffness, and disability. 4

But how much do you really need to lose? A study in Australia reported that participants who lost at least 7.7% of their initial body weight saw improvements in both function and symptoms. Based on the studied discussed here, it would appear that losing 7.7-10% of total body weight makes the most difference for people with symptomatic OA. 5

Where to Start

OA is not inevitable and can be prevented with lifestyle changes that address modifiable risk factors. Research shows that weight loss makes a meaningful difference for people who have or are at risk for developing OA.

It is important to talk with your primary care provider to determine if you are appropriate for physical activity. After that, you need to find a physical therapist who can treat your OA and help you with your weight loss goals.

At In Motion Physical Therapy, a holistic approach to treating OA is taken including manual therapy to address joint pain, aerobic activity to burn calories, and resistance training to strengthen the muscles surrounding the affected joint. Contact Dr. Lauren Schnidman for more information about how to maximize your function!


  1. Cibulka MT, Bloom NJ, Enseki KR, MacDonald CW, Woehrle J, McDonough CM. Hip pain and mobility deficits—hip osteoarthritis: revision 2017. J Orthop Sports Phys Ther. 2017; 47: A1– A37.
  2. Okifuji A, Hare BD. The association between chronic pain and obesity. J Pain Res. 2015;8:399–408. Published 2015 Jul 14. https://doi:10.2147/JPR.S55598
  3. Hall, M., Castelein, B., Wittoek, R., Calders, P. and Van Ginckel, A. (2019). Diet-induced weight loss alone or combined with exercise in overweight or obese people with knee osteoarthritis: A systematic review and meta-analysis. Seminars in Arthritis and Rheumatism, 48(5), pp.765-777.
  4. Gersing AS, Solka M, Joseph GB, et al. Progression of cartilage degeneration and clinical symptoms in obese and overweight individuals is dependent on the amount of weight loss: 48-month data from the Osteoarthritis Initiative. Osteoarthritis Cartilage. 2016;24(7):1126–1134. https://doi:10.1016/j.joca.2016.01.984
  5. Atukorala, I. , Makovey, J. , Lawler, L. , Messier, S. P., Bennell, K. and Hunter, D. J. (2016), Is There a Dose‐Response Relationship Between Weight Loss and Symptom Improvement in Persons With Knee Osteoarthritis? Arthritis Care & Research, 68: 1106-1114. https://doi:10.1002/acr.22805