One Thing I Learned about How Our Knee Works: Synovial Fluid/Joint Fluid

 Oct. 7, 2021

When is my last post? I don't remember. A cursory look shows it's Sept. 13. I went out for a 6 K walk in bare feet in the still of the night. It'd been a month and a half since I felt an unusual pain in my left knee. It'd had also been a week since I had it MRI-ed at an orthopedic clinic run by a childhood friend of mine. He said it's a damage in my left medial meniscus. The doc friend says it's a sign of aging. A dramatic improvement cannot be expected. It's advisable that I go easy and do my best to preserve the slowing deteriorating aging knee element of mine. That advice I accepted humbly. 

While my issue was diagnosed at the visit, prescription was suspended. The doc friend mentioned the most typical prescriptions such as a hyaluronic acid injection, but he said, "Knowing you, you probably do your own research, and figure out what's best for you." He is right. I consider an injection of lubricant as a symptomatic treatment and you can only expect a temporary relief without, of course, suggesting that a temporary relief is bad. But I am looking for something sustainable without the injection of an external substance. 

I studied the mechanisms of how parts of a knee work together to enable smooth movements. Here is one of a number of things that I learned. Or at least I think I have learned:

<Synovial Fluid/Joint Fluid （滑液[かつえき]）>

It was a ground-breaking realization that your knee joint is filled with liquid. Not just an ordinary kind of liquid, but a special kind of liquid that lubricates many components that comprise your knee so that they smoothly coordinate with one another. 

While one of its jobs is lubrication, this fluid has another important job, which is healing in nature. When a part that makes up your knee is damaged, it is soon detected by a sensor. Detection of a sign of damage, in turn, leads to an increase in the amount of synovial fluid. I understand this is what happened when my medial meniscus was damaged. My knee sort of swell with joint liquid. 

Though I am yet to discover a good medical explanation of this phenomenon, from the perspective of someone who actually experienced a knee injury, there seems to be a practical benefit to this swell. 

One, your knee mobility is significantly limited. For example, right after the injury it suddenly became so hard for me to bend the injured knee. It became impossible for me to sit straight. I have no problem with my right knee. But since I could not do the same on the left side, I had to throw the left leg straight forward to sit on the floor while having my right knee fully bent with the heel touching the right hip with any problem. 

Immobility of the damaged knee works favorably for recovery, I presume. While no further damage is inflicted, my body's construction workers can concentrate on their repair work, procuring concrete blocks of calcium to the construction site and building them one next to and on top of another with cement. 

Compare the above situation with the same construction workers having to work in a tropical storm or scorching summer heat. Do you think they can work efficiently? Probably not. Therefore, an increase in synovial fluid achieve the dual purpose of creating inconvenient immobility for the patient and a convenient work environment for the physiological agents that are responsible for healing the damage!