This has been a decennium horribilis (horrible decade) for knee arthroscopy research, showing in study after study that common knee surgeries don't work. Why is this? While there could be many reasons, I'd like to propose a new one: the surgery kills stem cells in the knee that are needed to maintain the health of the joint.
Does the Knee Have Stem Cells?
It might surprise you that your knee has resident stem cells. In fact, it has stem cells that live in the fat pads and the synovial fluid and membranes. What do they do? They're likely involved in the maintenance of the joint tissues, such as ligaments, cartilage, and meniscus. Hence, keeping those stem cells in tip-top shape would be important.
What Happens During Knee Arthroscopy?
Knee arthroscopy is one of the most common surgical procedures in the United States and in many developed countries. It involves filling the knee joint with water, making incisions in the skin, inserting an arthroscope, cutting out things that are in the way to improve the view, and then either looking around and/or doing something. In order to optimize the view, as things like cutting, stitching, or placing implants are accomplished, the joint is irrigated with a constant flow of water.
Irrigation of the Knee Reduces Resident Stem Cells
A new study was just published on the use of a device to dislodge stem cells during knee arthroscopy. While the reason to use the device is questionable, one of the most interesting findings was that irrigation of the knee during knee arthroscopy depleted the stem cell content by 400%! This makes sense, as we have water flowing aggressively through the joint for most of the procedure. Here's what the study authors said:
"Samples of subsequent irrigation fluid indicated that MSC numbers on average decreased 4-fold over the course of surgery, suggesting that standard orthopaedic practice depletes the joint of stem cells."
Major Stem Cell Reservoirs of the Knee Are "In the Way," So Parts of Them Are Commonly Removed
We've known for some time that the fat pads within the knee have loads of stem cells (ref 1, ref 2, ref 3). Prior to these discoveries, it used to be thought that these fat pads functioned only as a cushion. However, not everyone has gotten the memo that they may be critical for the health of the knee.
For example, when an arthroscope is first placed in a joint, many times the infrapatellar fat pad is in the way. Hence, parts of it can be removed to improve the view. In addition, there's another fat pad that can surround the ACL ligament and yet another around the kneecap. So any removal of any of these fat pads is likely not helping anybody.
Surgeons Commonly Inject Toxic Substances
Many surgeons typically inject steroids or Marcaine to reduce inflammation or to provide anesthesia after the procedure. However, these substances are now known to kill stem cells. So why is this still being done?
Most surgeons believe that steroids are harmless. The problem is that the doses commonly used are way too high (by about 1 million times). In the nanogram-dose range, they're not harmful and may help stem cells. In the one-million-times-too-concentrated version (milligram), steroids are toxic to stem cells.
In my experience, most surgeons also don't know that some local anesthetics are toxic to stem cells. For example, common local anesthetics, like Marcaine and lidocaine, can kill stem cells dead at low doses. For Marcaine, that's ultralow levels.
So What Can You Do to Protect Yourself?
First, the research shows that many knee arthroscopy procedures, like debridement and meniscectomy, are ineffective, so please don't sign up for these procedures. Second, if you really need these procedures, here's what you should request:
1. Gas arthroscopy—most surgeons have abandoned it, but you can do this procedure without depleting the stem cell content through irrigation. There was a concern early on about air embolism, but it turns out that when low pressures are used, these concerns were overblown and that gas may actually reduce the patients postop pain.
2. No removal of fat-pad tissue—the surgery may take longer and be more technically difficult, but your knee may thank you.
3. Avoid all toxic anti-inflammatories and anesthetics—your surgeon can inject specially compounded nanogram anti-inflammatories and ropivacaine (an anesthetic that's more stem cell friendly that's normally used in labor-and-delivery wards).
The upshot? You likely don't need the knee surgery that's being recommended. However, if you do, then please make sure the surgeon doesn't kill any of your natural stem cells in the knee. You need every one of those you can get!