Hip and knee replacements are some of the most frequently performed and effective surgeries worldwide. The main indication for hip and knee replacement (joint replacement surgery) is osteoarthritis, which leads to reduced function and quality of life.
Osteoarthritis is a degenerative form of arthritis characterised by the wearing down of cartilage that cushions and smooths the movement of joints – most commonly for the hip and knee. It causes pain, swelling and stiffness, resulting in a loss of mobility and function. Osteoarthritis is one of the ten most disabling diseases in developed countries. Worldwide, estimates show that 10% of men and 18% of women aged over 60 have symptomatic osteoarthritis, including moderate and severe forms (WHO, 2014[23]).
Age is the strongest predictor of the development and progression of osteoarthritis. It is more common in women, increasing after the age of 50, especially in the hand and knee. Other risk factors include obesity, physical inactivity, smoking, excessive alcohol consumption and injuries. While joint replacement surgery is mainly carried out among people aged 60 and over, it can also be performed on people at younger ages.
In 2019, Germany, Switzerland, Austria, Finland and Belgium were among the countries with the highest rates for hip and knee replacement (Figure 5.25 and Figure 5.26). The OECD averages are 174 per 100 000 population for hip replacement, and 137 per 100 000 for knee replacement. Mexico, Costa Rica, Chile, Portugal, Israel and Ireland have low hip and knee replacement rates. Differences in population structure may explain part of this variation across countries, and age standardisation reduces it to some extent. Nevertheless, large differences persist, and the country ranking does not change significantly after age standardisation (McPherson, Gon and Scott, 2013[24]).
National averages can mask important variation in hip and knee replacement rates within countries. In Australia, Canada, Germany, France and Italy, the rate of knee replacement is more than twice as high in some regions than others, even after age standardisation (OECD, 2014[25]). Alongside the number of operations, the quality of hip and knee surgery (see indicator “Hip and knee surgery” in Chapter 6) and waiting times (see indicator “Waiting times for elective surgery”) are also critical for patients.
Since 2009, the number of hip and knee replacements has increased rapidly in most OECD countries (Figure 5.27 and Figure 5.28). On average, hip replacement rates increased by 22% between 2009 and 2019 and knee replacement rates by 35%. This aligns with the rising incidence and prevalence of osteoarthritis, caused by ageing populations and growing obesity rates in OECD countries. For example, in the United States, the prevalence of knee osteoarthritis has more than doubled since the mid-twentieth century (Wallace et al., 2017[26]). Most OECD countries show increasing trends of varying degrees, but Ireland shows slower growth than the average for both hip and knee replacements, while Italy shows above‑average growth.
In 2020, however, initial data from a few OECD countries show sharp declines in hip and knee surgeries. This reflects the fact that postponing non-urgent elective surgery was a key measure adopted by countries to increase health systems’ capacity to anticipate and address the COVID‑19 surge. For example, data from 2020 show a more than 20% drop in hip replacements in Ireland and Italy, and a more than 10% drop in Norway and the Czech Republic compared to 2019. Knee replacements fell by around 30% in Italy, Ireland and the Czech Republic in 2020 compared to 2019, and by 8% in Norway.
