Effect of Obesity on Knee Osteoarthritis Symptoms and Surgical Outcomes

The Role of Weight Loss in Knee Osteoarthritis Management

Obesity is a serious health problem that increases a patient’s risk for many chronic conditions, including joint pain and knee OA. In 2018, the prevalence of obesity in the United States was 42.4%.8 Patients with a BMI ≥30 have a 7-fold increased risk of developing knee OA.2

Weight loss is a healthy way to manage symptoms associated with knee OA. Research shows that weight loss is associated with reduced pain, improved function, and better quality of life in patients with knee OA who are overweight or obese.9,10 There is a strong, consistent relationship between obesity and the development of severe OA knee pain; clinicians can use this information to educate patients about the importance of weight loss to modify the disease course.11 Clinicians should educate patients about how much weight they may need to lose to see an improvement in knee OA symptoms.

Messier et al found that for every 1 pound lost, 4 pounds of stress are unloaded off the knees.12 A body weight reduction of 1% has been associated with a 2.8% improvement in function, pain, and stiffness, as measured by the Western Ontario and McMaster Universities Arthritis Index (WOMAC) scale.10 Thus, overweight or obese patients with knee OA who reduce their weight by 10% could see a 28% decline in knee OA pain and symptoms.10

It is important for patients to understand that weight loss will not reverse the disease process but can alter the severity of their symptoms by reducing the load on the knees. Daugaard showed that patients with obesity who lost a substantial amount of weight (mean, 12 kg) reduced their pain level.13 However, the inflammation seen on dynamic contrast-enhanced magnetic resonance imaging was unchanged from the start of the study.

Weight loss also can help prevent the progression of mild knee pain to severe, debilitating knee pain. JInks et al found that 19% of new cases of severe knee pain that developed over the 3-year study period in patients who were overweight or obese could have been avoided by a shift downward in BMI category.11 This demonstrates that weight loss is an effective treatment option to improve quality of life and delay surgical intervention. Early intervention by clinical providers focused on educating patients about weight-loss benefits can help those with knee OA maintain the ability to continue their normal daily activities without disabling pain.

Obesity and Knee Surgery Outcomes

When daily functioning is impacted by severe OA pain that is refractory to conservative intervention, surgical intervention becomes a viable option. Total knee replacement is an invasive procedure, and providers and patients must evaluate the risks and benefits of this surgery. For patients who eventually need surgical intervention for knee OA, weight loss also leads to improved outcomes after TKR surgery.

Patients with obesity are at increased risk for surgical revision.14,15 Surgical revisions can be required after loosening or wear of 1 or more components of the prosthetic joint.14 Higher revision rates in patients with obesity have been attributed to increased compressive forces on the joint due to excess weight. Surgical revision of a TKR also may be needed after complications from an infected prosthetic joint.14 Such infections after TKR are more common in patients with obesity compared with patients without obesity.14,15 This is, in part, because obesity is associated with reduced subcutaneous tissue oxygenation, which is associated with higher rates of wound infection.16 The severity of potential postoperative infections can range from a superficial wound infection to deep infection of the prosthetic joint. Studies have shown that patients with obesity who undergo TKR are at increased risk for both deep infections and TKA revisions.15

Despite the possibility of complications, TKR has been proven to improve functional outcomes in patients with and without obesity.

How to Help Patients Lose Weight

When addressing weight loss with patients, it is important to provide them with feasible weight-loss options that can help them achieve their goals. Clinicians must assess each patient’s needs and access to resources to help them achieve optimal outcomes when they are attempting to lose weight.

Initial weight-loss recommendations should include information on how patients can increase physical activity while also modifying their diet to reduce caloric intake. An open discussion about obstacles to achieving weight loss will allow patients and providers to come up with feasible lifestyle modifications patients can incorporate into their daily routines.

Patients have reported that lack of time and lack of accessibility to an exercise facility are 2 of the most common barriers preventing them from losing weight.17 For patients without access to a gym, clinicians can provide home exercises that require little equipment. For patients who do have access to exercise facilities, aquatic therapy has proven to be an effective option for individuals with knee OA.8 Patients who have concerns about how they will achieve exercise or who experience low physical self-esteem may benefit from group exercise programs or a personal trainer.

For patients to achieve weight loss, they must address diet as well as exercise habits. Information about healthy eating and cost-efficient healthy recipes can provide patients with the skills and resources needed to incorporate healthy eating habits into their daily routines. In a survey conducted at an orthopedic clinic, 61% of participants with obesity reported that they would be most interested in information about healthy eating when receiving information from a healthcare professional about weight loss.18

Teaching patients how to moderate portions and eliminate unhealthy foods from their diet also is positively associated with successful weight loss. Some patients may benefit from a referral to a registered dietitian when starting their weight-loss journey. Reducing caloric intake by decreasing sugar consumption, increasing fruit and vegetable intake, controlling portions, and increasing physical activity provide patients with the greatest chance of achieving weight loss.19
Pharmacotherapy is an option for patients with a high BMI and weight-related comorbidities who have tried and failed to lose weight with exercise and diet alone. A recent meta-analysis of randomized controlled trials found that the following antiobesity medications indicated for long-term use are associated with a significant reduction in body weight: liraglutide, lorcaserin, naltrexone/bupropion, orlistat, and phentermine/extended-release topiramate.20 Primary care providers should discuss these options with their patients to determine whether these options are appropriate.

When conservative treatment options have failed, referral to a bariatric surgeon may be warranted.

This article originally appeared on Clinical Advisor