Windswept deformity of the knee: prevalence and predictive factors in osteoarthritic and healthy populations

Listen to Simon and Amy discuss the paper 'Windswept deformity of the knee: prevalence and predictive factors in osteoarthritic and healthy populations' published in the October 2024 issue of Bone & Joint Open.

Click here to read the paper.

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Transcript

[00:00:00] Welcome back to another episode of AI Talks with Bone & Joint from the publishers of Bone & Joint Open. Today we're discussing the paper, 'Windswept deformity of the knee: prevalence and predictive factors in osteoarthritic and healthy populations', published in October 2024 by J. Moore, V. A. Van de Graaff, J. A. Wood, P. Humberg, W. Colin, J. Belmans, D. B. Chen and S. J. McDessie. 

I am Simon and I'm joined by my co-host Amy. 

Hello Simon, delighted to be here. This is indeed an intriguing study to explore. Windswept deformity, or WSD, is characterised by a varus alignment in one knee and a valgus alignment in the other, and this study delves into its prevalence and contributing factors in both osteoarthritic and healthy populations.

Let's begin with the motivations behind the research. The authors were particularly keen to understand how prevalent WSD is among those with osteoarthritis, compared to those without, and what factors might account for these differences. [00:01:00] Despite its distinctive presentation, there was scant large sample data on its prevalence and causes, particularly in adults.

Indeed, they carried out a case control radiological study comparing 500 healthy knees and 710 osteoarthritic knees. The healthy participants were aged between 20 and 27 years, while the osteoarthritic participants were generally older, with a mean age of 70.2 years, and were undergoing bilateral total knee arthroplasty.

They measured several angles, including the mechanical hip knee ankle angle, MHKA, medial proximal tibial angle, MPTA, and Lateral Distal Femoral Angle, LDFA, to determine alignment. Notably, WSD was defined as having a varus MHKA of less than minus two degrees in one limb, and a valgus MHKA of more than two degrees in the other

The findings were quite striking. WSD was far more prevalent in the osteoarthritis group compared to the healthy group, [00:02:00] 7.9 percent versus just 0.4%, with the relative risk nearly 20 times higher in the osteoarthritis group. One of the main conclusions was that WSD is predominantly an acquired condition post skeletal maturity, rather than a congenital one. They identified meniscectomy, rheumatoid arthritis and osteotomy as significant predictors of WSD within the osteoarthritis group.

They employed backwards logistic regression to demonstrate that individuals who had undergone a meniscectomy, for example, had odds ratios indicating a fourfold increase in the likelihood of developing WSD. Rheumatoid arthritis and prior osteotomy were also key predictors. 

It's also pertinent to note that they discovered different impacts based on the type of meniscectomy. For instance, those with a history of medial meniscectomy were more likely to exhibit varus alignment, whereas individuals with a lateral meniscectomy tended towards valgus alignment. Yes, and this adds an additional layer of complexity to the already nuanced relationship between knee surgery and [00:03:00] deformity.

The study mentioned that 53.6 percent of WSD patients had undergone meniscectomy, compared to 29.9 percent in the overall osteoarthritis cohort, emphasising the significant role such surgeries play. 

The researchers also highlighted how osteoarthritis can lead to a progression in the MHKA. Essentially, as arthritis progresses, the mechanical alignment of the knee can continue to deteriorate.

They substantiated this with statistics showing that the mean MHKA in healthy individuals was minus 1.3 degrees, while in the osteoarthritis group it was minus 3.8 degrees. This underscores the severe impact of osteoarthritis on knee alignment. 

In summary, this study not only illuminated the prevalence of windswept deformity in osteoarthritic patients, but also identified key factors that contribute to its development. It underscores the importance of considering past surgical history, like meniscectomy, when treating osteoarthritis. 

Absolutely. [00:04:00] It's essential for clinicians to be aware of these findings to better understand and potentially mitigate the development of WSD in osteoarthritic patients. This study significantly enhances our knowledge of knee deformities and their management.

Well that's all the time we have for today. Thanks for joining us on this episode of AI Talks with Bone & Joint. Stay tuned for more in depth discussions on the latest research in bone and joint science. Thank you everyone. Until next time.