A new study published online on 17 January in the journal Arthritis & Rheumatism reports that rates of knee replacement surgery in Finland’s 30 to 59-year-olds soared between 1980 and 2006, with women being the more common recipients throughout. Lead author Dr. Jarkko Leskinen, an orthopedic surgeon at Helsinki University Central Hospital, and colleagues also report that the greatest increase was among those aged between 50 and 59.

Knee replacement surgery is the common term for partial and total knee arthroplasty, an operation where part or all of the diseased or damaged surfaces of the knee joint are replaced with metal and plastic parts shaped to allow the patient to move the knee normally.

Arthroplasty is often the only treatment option for people who have severe osteoarthritis (OA) of the knee, as Leskinen explained the press:

“OA risk is shown to increase with age and for severe knee OA arthroplasty is a commonly used treatment option when patients are unresponsive to more conservative therapies.”

But although arthroplasty has become increasingly more common, we don’t have much information on rates among different parts of the population, and its effects in younger patients.

For their study, Leskinen and collegues looked at records of all unicondylar (partial) and total knee replacements performed between 1980 and 2006 in Finland. These records are kept by the Finnish Arthroplasty Registry.

They looked at how incidence rates of arthroplasty for knee osteoarthritis varied by gender, age, and hospital volume.

Their main findings show that:

  • Rates of total knee replacement among those aged 30 to 59 went up 130-fold in the 27-year period.
  • The incidence went up from 0.5 procedures per 100,000 of Finland’s population to 65 per 100,000.
  • The fastest rise happenend between 2001 and 2006 (from 18 to 65 per 100,000).
  • There was a similar rapid rise in partial knee replacements: from 0.2 to 10 procedures per 100,000 of the population.
  • In the last ten years of the study (1997 to 2006), the rate of total knee replacements was 1.6 to 2.4 times higher in women than in men.
  • The rates of total and partial knee replacements were highest among 50 to 59-year-olds.

The researchers conclude that their study demonstrates “the rapid increase in incidences of arthroplasty among patients with primary knee osteoarthritis in Finland, especially in age group of 50 to 59 years of aged.”

“There was no single explanatory factor behind this phenomenon though some of the growth might be due to the increase of incidences observed in low and intermediate volume hospitals,” they note.

Leskinen said:

“Given that younger patients may be at higher risk of artificial knee joint failure and thus in need of a second replacement surgery, long-term data are needed before widespread use of total knee arthroplasty is recommended for this patient population.”

In an accompanying editorial, Dr. Elena Losina, of Brigham and Women’s Hospital and Harvard Medical School in Boston, Massachusetts, agrees with Leskinen. She writes that total knee replacement is an effective treatment for OA in older patients, those in their 60s, 70s and 80s.

“However, past performance may not guarantee future success, and with an increasing number of knee replacement recipients under 60 years old, more intensive study of arthroplasty outcomes in younger patients is warranted,” she urges.

According to the World Health Organization (WHO), osteoarthritis is the fourth leading cause of years lived with disability worldwide.

Experts estimate that around 10 million people are living with osteoarthritis in the US, where over 600,000 knee replacements were carried out in 2009, according to a report from the Agency for Healthcare Research and Quality. A previous study estimated that by 2030 the number of such procedures could grow by over 670% to nearly 3.5 million a year.

Written by Catharine Paddock PhD