Knee injections (Hyaluronan Injections or viscosupplementation) are a procedure in which medication is directly injected into the knee joint to treat pain.
The knee joint normally contains a thick gel called synovial fluid. Synovial fluid is responsible for lubricating joints, acting as a shock absorber and it allowing the bones to glide smoothly. 
Knee pain can originate from a ligament or tendon injury, broken bones, osteoarthritis, inflammatory arthritis or septic arthritis.  These injuries and conditions cause the articular cartilage and meniscus to break down and the synovial fluid becomes less viscous;  so, the synovial fluid doesn’t do it job of absorbing the shock and providing protection for your knee.
Knee gel injections objectives include using a synthetic gel, similar to the natural synovial fluid, in order to: increase lubrication, reduce creaking, grinding, control inflammation, restore function and decrease pain. 
In 1997 the FDA approved Synvisc One, the first gel injection.  Today, there are over six different brands available, all of which are equally effective.
Why is Viscosupplementation done?
There are a variety of options when it comes to treating knee pain and knee osteoarthritis including: oral pain medications, steroid injections, physical therapy, and lifestyle changes. Knee gel shots are another great option.
When the synovial fluid breaks down due to trauma like sports injuries, or just age-related wear-and-tear, there is increased joint pain, stiffness and could be a sign of onset or worsening of osteoarthritis. Knee arthritis can lead to chronic pain, stiffness, decreased range of motion and affects the activities you enjoy.
The goals of treating knee osteoarthritis with viscosupplementation include:
Reducing knee pain
Improving range of motion
Increasing lubrication in the knee
Possibly slowing the progression of knee osteoarthritis
Patients seek knee gel shots because:
It is better at decreasing knee pain than over-the-counter medications (like acetaminophen). 
It lasts longer. Research shows that pain relief lasts up to six months on average and may last up to two years. 
It is an alternative for people who have knee pain but are not candidates for a knee replacement.
Research suggests that knee gel shot injections can stimulate the body to produce more hyaluronic acid naturally, which helps keep the remaining cartilage healthy and keeps the knee functioning.
Allergic reaction (especially with egg or poultry allergies) ß Euflexxa is safe for people with these allergies
pseudo septic reaction (red, swollen, tender)
If you experience any side effects that are persistent, please call the office.
How you prepare for a knee injection
There aren’t any special preparations for gel shot injections in the knee, just be sure to inform your provider about all the medications you are taking, medical conditions and if you have felt feverish in the past 14 days. There are no dietary restrictions when getting a knee gel shot.
How are Knee gel shots administered?
Hyaluronic acid can be broken down in the stomach by enzymes; so, a pill form is not available. Viscosupplementation can only be performed via an injection route.
Viscosupplementation is a quick procedure that takes about 30 seconds.
The area to be injected is cleaned and sanitized.
Either a local anesthetic is injected in the area around the knee joint or a spray is used to numb the area.
Sometimes, imaging such as ultrasound is used in order to visualize the exact spot.
A needle is inserted under the kneecap from the side directly into the joint space and the viscosupplementation is pushed into the joint.
A small bandage is applied over the injection site.
Depending on the brand of knee gel shots used, there will be between three and five injections over the following several weeks usually done 1 week apart.
While not all patients experience relief with viscosupplementation, many patients report a decrease in pain over the following 3-5 weeks with the most significant level of pain relief coming two to three months after the first injection.
After a Knee injection
Patients are monitored up to 30 minutes after the procedure to make sure there are no reactions to the medicine before they are released.
Most patients who receive viscosupplementation only have minor pain at the injection site; however, swelling, warmth and bruising around the joint can also occur. These minor side effects are short-lived and can be relieved with an ice pack. If symptoms do not resolve, make sure to contact the office.
Knee injections success rates – does it work?
Knee gel shot injections don’t stop the knee osteoarthritis from progressing; but research suggests that hyaluronic acid injections in the knee do work to decrease pain.  A 2020 meta-analysis came to a conclusion that injecting hyaluronic acid decreased pain and improved function in people with knee osteoarthritis.  Research further demonstrates Knee gel shots improve function, decrease stiffness, and decreases pain without using a steroid. 
How long does it take for a knee gel shot to work?
Hyaluronic acid injections are not like cortisone injections, gel shots in your knee are slower acting and it may take a few weeks before you feel it working.
While it depends upon the medication used, research shows the best results from viscosupplementation occur between the fifth and thirteenth weeks. 
How long do the injections last?
While gel knee injections can take longer to work than cortisone injections, they do last a lot longer—around six months. A significant difference compared to cortisone shots that provide quick relief but is short lived.
Webb, D., & Naidoo, P. (2018). Viscosupplementation for knee osteoarthritis: a focus on Hylan G-F 20. Orthopedic Research and Reviews, Volume 10, 73–81. https://doi.org/10.2147/orr.s174649
Adams, M. E., Atkinson, M. H., Lussier, A. J., Schulz, J. I., Siminovitch, K. A., Wade, J. P., & Zummer, M. (1995). The role of viscosupplementation with hylan G-F 20 (Synvisc®) in the treatment of osteoarthritis of the knee: a Canadian multicenter trial comparing hylan G-F 20 alone, hylan G-F 20 with non-steroidal anti-inflammatory drugs (NSAIDs) and NSAIDs alone. Osteoarthritis and Cartilage, 3(4), 213–225. https://doi.org/10.1016/s1063-4584(05)80013-5
Kemper, F., Gebhardt, U., Meng, T., & Murray, C. (2005). Tolerability and short-term effectiveness of hylan G‐F 20 in 4253 patients with osteoarthritis of the knee in clinical practice. Current Medical Research and Opinion, 21(8), 1261–1269. https://doi.org/10.1185/030079905x56501
Phillips, M., Vannabouathong, C., Devji, T., Patel, R., Gomes, Z., Patel, A., Dixon, M., & Bhandari, M. (2020). Differentiating factors of intra-articular injectables have a meaningful impact on knee osteoarthritis outcomes: a network meta-analysis. Knee Surgery, Sports Traumatology, Arthroscopy, 28(9), 3031–3039. https://doi.org/10.1007/s00167-019-05763-1