Weight-loss reduces patellofemoral loading and thus arthritis
Knee pain and arthritis are one of the most common causes of disability. Knee pain and arthritis of the knees are actually a part of the same spectrum or a continuum. Knee arthritis or osteoarthritis is most commonly caused by chronic wear and tear of overuse such as occurs when you are carrying too much weight or have a repetitive motion such as jumping. The image to the right is an x-ray (from orthoinfo.aaos.org) showing severe osteoarthritis. In my experience, knee pain magnifies itself. What I mean by this is that knee pain causes less activity which causes more obesity which causes more knee pain. You can quickly see why knee pain and osteoarthritis can lead to the ever-expanding waistline over time. The unfortunate thing is that most people who develop osteoarthritis of the knees slowly reduce their exercise which makes the problem worse. Osteoarthritis actually improves with exercise is small is the osteoarthritis is not severe. Once a patient gets to the level of severe osteoarthritis the only treatment is injections or knee replacement. The question my mind has always been what is the efficacy of weight-loss in overweight and obese adults with tibiofemoral (knee) osteoarthritis.
A recent study illustrates a novel solution. Weight loss is an approach that almost always works at reducing knee pain. This study was published in the Journal: Osteoarthritis and Cartilage. The study behind the journal article was a single-blind randomized clinical trial called the Intensive Diet and Exercise for Arthritis (IDEA). The purpose of this study was to determine whether weight loss induced by diet, with and without exercise, could reduce the stress on the patellofemoral joint and thus result in less osteoarthritis in overweight and obese patients. For these secondary analyses, researchers used data from the IDEA participants. IDEA excluded potential participants with severe radiographic evidence of knee osteoarthritis because it might limit the ability for patients to actually be successful at weight loss. Participants were randomized to three groups: diet only (69), exercise only (69), and diet & exercise (67). The interventions were delivered over an 18-months period. The participants were assessed for all outcome at baseline, 6-months, and 18-months. The biomechanical outcomes of interest during walking included peak patellofemoral compressive force and patellofemoral joint compressive force impulse during the stance phase of walking. The researchers found that all three groups showed significant decreases in patellofemoral compressive force and impulse with the weight-loss. In particular, participants in the diet-only group and those in diet and exercise group had greater weight-loss compared to the participants in the exercise only group. This makes sense because most weight loss occurs in the kitchen and not the gym.
The results of the study only make sense because if you put an M1 tank on a Yugo chassis, the wear and tear will quickly wear out the chassis.
The bottom line: Weight-loss induced by diet, with or without exercise, or with exercise alone, reduced knee joint compressive loading during walking after accounting for the change in weight. Weight-loss has a direct effect on reducing tibiofemoral compressive force and thus likely reduces osteoarthritis over time. I recommend weight loss to all patients with lower extremity joint pain and back pain. Further research is warranted.