Unlocking the Mystery: Why Prolonged Sitting May Lead to Knee Swelling!

Farewell to the hands-and-feet era of decades past; we're now in the age of prolonged sitting dominated by electronic devices. In today's society, where sitting for extended periods is the norm, knee health often takes a back seat. From prolonged hours at desks to immersion in the digital world, sitting has seamlessly become part of our daily lives. Yet, the damage it inflicts on our knees is more alarming than we realize. Join us in today's clinical story to explore the link between prolonged sitting and knee health, and discover ways to protect your knees.

Today, I'd like to share a story that happened last Sunday involving my "neighbor aunt," who is in her 60s. She had recently taken a long flight and noticed some swelling on both sides of her knees upon arrival. Dismissing it initially, she found the swelling subsided on its own after a few days.

Despite having a good habit of walking for about half an hour every day, on Saturday, she spent nearly 6-7 hours sitting continuously in front of the computer for office work. The next morning, both her knees, especially the right one, were in unbearable pain along with swelling.

Neighbor Aunt approached me, opened the door, and as soon as it swung open, I immediately noticed the significant swelling on her right knee—impossible to fully straighten. In contrast, her left knee appeared straight with only a slight swelling. Concerned, she hastily asked:

"Rex, I didn't do anything unusual. I walk for over 30 minutes every day without issues. I just sat continuously for 6-7 hours without putting weight on my knees. Why did they swell up so severely the next day, and why is it so painful?"

"My dear neighbor," I responded, "when you keep saying you haven't been sitting much, watch out – the devil's in the details," emphasizing the subtleties of our habits.

"Sitting all day is like a silent killer, and it might even be worse than smoking."

When we think sitting for a long time is no big deal, the real issue is that our knees have to stay at a 90-degree angle. It's not just about the 90 degrees; what's really scary is having to keep your knees still in that 90-degree position for a long time.

If you were to search advice from various online experts using the term "best sitting posture," you'd likely find around 10 recommended positions. Interestingly, about 9 out of 10 would suggest keeping your knees at the classic ninety-degree angle. However, here's the thing – that's the significant "mistake in the mix." Why? Well, it seems we're all treating our knees like they're the unsung heroes, overlooked while the spotlight is on maintaining the lower back and neck posture for “good alignment.”
 

"Knees are essentially the second liver for humans, silently enduring the abuse inflicted upon them."

Let's Talk about the 'Why' and 'How' Behind :

Poor Blood Flow During Prolonged Sitting:

• Apart from the increased pressure due to bending, another potential issue during prolonged sitting is "local tissue ischemia" [2]. Research suggests that when people with knee pain sit with their knees bent at 90 degrees, the blood flow to the knee decreases, indicating a problem with poor blood supply to the area. This might also be linked to the development of knee pain and swelling.

Increased Pressure Between Knee Bones

• The reason for our neighbor aunt's knee pain and swelling is quite clear in both early and recent studies [1][2]. When you keep your knee bent at 90 degrees for an extended time, the pressure inside the knee bone is much higher than when it's fully straight. This elevated pressure is particularly noticeable in individuals who already had knee pain, making their knee bone pressure significantly higher than those without knee pain.

Alright, how do we address our neighbor aunt's issue?

If prolonged sitting is causing an increase in intraosseous pressure in the knee, the solution lies in relieving this pressure. The key to alleviating pressure is simple :

KEEP THE KNEES STRAIGHT/ EXTENDED.

Therefore, the exercises I recommended for our neighbor aunt are:

• Seated Calf Stretch
  • Sit with your knees extended, stretch your calves, and keep your knee straight.

• Quad Sets
  • Repeatedly perform Quad Sets, which involve contracting the quadriceps muscles (I find the term "Quad Sets" a bit tongue-twisting, so let's just call it the "Call Me King" or King exercise because the quad is the king - because the quadriceps are responsible for the maximum stability and extension of the knee.

     

     

     

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    A post shared by Dr.Rex Chen PT,DPT,OCS,FAAOMPT (@ptrex_sportsmed)

• Elevate Your Knees While Sleeping, Focusing on Swelling
  • Elevate your knees while sleeping and consider incorporating simple knee compression techniques, such as using a knee brace, to enhance local blood circulation around the knees and address swelling issues. 

I hope through this piece, everyone realizes how we inadvertently harm some silent organs in our daily lives—sometimes it's the liver, sometimes it's the knees. If we pay more attention, I believe our bodies can naturally and properly recover with the right healthcare approaches, restoring health and functionality!

^{Reference
[1]Ho KY, Hu HH, Colletti PM, Powers CM. Rec-reational runners with patellofemoral pain exhibit elevated patella water content. Magn Reson Imaging. 2014;32:965-968. http://dx.doi.org/10.1016/j.mri.2014.04.018} 

^{[2]Näslund J, Waldén M, Lindberg LG. Decreased pulsatile blood flow in the patella in patel-lofemoral pain syndrome. Am J Sports Med. 2007;35:1668-1673. http://dx.doi.org/10.1177/0363546507303115}