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Knee osteoarthritis is a disorder that involves age–related changes to the cartilage in a knee joint. In a normal knee, the ends of each bone are covered by cartilage, a smooth substance that protects the bones from one another and absorbs shock during impact. In knee osteoarthritis, this cartilage becomes stiff and loses its elasticity, which makes it more vulnerable to damage. Cartilage may begin to wear away over time, which greatly reduces its ability to absorb shock and increases the chances that bones will touch one another. When this occurs, it typically results in pain within and around the knee that gets worse with activities like walking, going up/down stairs, or sitting/standing. Swelling, tenderness, and stiffness are also common.

Although no treatment can slow or stop this loss of cartilage, physical therapy is strongly recommended as an initial intervention for all cases of knee osteoarthritis. Undergoing a comprehensive course of physical therapy can help reduce pain levels and preserve knee function through movement–based strategies like stretching and strengthening exercises, hands–on therapy, bracing, and recommendations on how to modify pain–inducing activities. Physical therapy can also reduce the need for other interventions that may be potentially unnecessary or dangerous, such as surgery or opioids, and research has shown that the earlier physical therapy is initiated, the greater its benefits.

Despite these recommendations, many patients with knee osteoarthritis either never see a physical therapist or fail to do so until much time has passed, which can lead to worse outcomes. With this in mind, a study was conducted to investigate whether there is an association between early versus late initiation of physical therapy for knee osteoarthritis and the future use of opioids.

For the study, investigators searched Medicare and commercial health insurance claims data from 1999 to 2018 for information on adults with knee osteoarthritis who were referred to physical therapy within one year of their diagnosis. Patients identified through this search were then categorized as either “opioid naïve” (meaning they did not use opioids) or “opioid experienced” based on prescription history with these drugs before initiating physical therapy for knee osteoarthritis. Finally, researchers examined the relationship between when physical therapy was initiated and with the use of opioids—including chronic opioid use—over 1 year.

Researchers identified 67,245 patients with knee osteoarthritis, 35,899 of whom were classified as “opioid naïve” and 31,346 of whom were “opioid experienced.” In the opioid naïve group, the risk for any opioid use was higher for patients that delayed starting physical therapy compared to those who began within one month of their diagnosis, and this risk continued to increase as the length of the delay grew (up to 12 months). Similar results were found for the risk of chronic opioid use, which was 2.5 times higher for patients who waited 9–12 months to see a physical therapist compared to those who started physical therapy within one month. The same trends were identified in the opioid experienced group, with increased risks for both opioid use overall and chronic opioid use in patients who waited to see a physical therapist versus those who saw one within one month.

These findings suggest that delaying the start of physical therapy may increase the risk for using opioids compared to starting it early (within one month) for patients with knee osteoarthritis, and the longer the delay, the greater the risk for opioid use. Therefore, if you’re currently dealing with knee osteoarthritis, we strongly recommend that you visit a physical therapist sooner rather than later.