Brief introduction of knee joint cavity injection: how to select the appropriate injection method
||KEY POINTS FOR TODAY：
• The standard treatments for knee pain include physical therapy, weight loss, and medication.
• When the above standard therapy fails, intra-articular injection can be used.
• However, for intra-articular injection, only the research data support the injection of steroids, while the data support for other injection types is limited.
Osteoarthritis (OA), also known as degenerative joint disease, is the most common arthritis. At present, the treatment of knee osteoarthritis includes physical therapy, weight loss, medicine and intra-articular injection. The drugs mainly include NSAIDs, capsaicin cream and menthol cream.
• NSAIDs：
--Diclofenac gel, diclofenac patch, etc
--Oral ibuprofen
--Oral meloxicam
--Oral naproxen, etc
• Capsaicin cream:
• Menthol cream:
For patients who fail to respond to the above standard therapy, intra-articular injection may be considered. At present, there are 5 methods of intra-articular injection.
• Intraarticular injection:
--Steroid injection;
--Hyaluronic acid gel injection;
--Platelet rich plasma injection;
--Autologous serum injection;
--Stem cell injection
However, the American Academy of Orthopaedic Surgeons (AAOS) (Rf: 1) and the American College of Rheumatology (ACR) (Rf: 2) only recommend steroid injection, because other types of injections lack sufficient clinical data support.
1：Steroid injection (triamcinolone acetonide)
Steroid injection can provide short-term pain relief. Compared with oral steroid drugs, intra-articular steroid injection has less side effects. In addition, mixed injection of steroids and lidocaine can also relieve pain. Steroid injection can relieve pain for 1 to several weeks, and generally it can be injected once every 3 months at most. However, it is not recommended to continuously inject every 3 months, because it will accelerate cartilage loss. It is better to inject 1-2 times within a year.
At present, there are two kinds of steroid injections: short-term (triamcinolone acetonide injection) and long-term (triamcinolone acetonide sustained-release injection suspension). The original research company of triamcinolone acetonide sustained-release injection suspension is Flexion Therapeutics, with the trade name of Zilretta, which was approved for listing on October 6, 2017.
2：Hyaluronic acid gel injection (mucus supplement)
Hyaluronic acid is a natural lubricant in the joints, but it will be lost with age, so injection into the joint cavity can replace the lost hyaluronic acid. Existing HYALGAN ® Hyaluronic acid injection, Synvisc and Euflexxa, etc.
However, a meta-analysis showed (Rf: 3) that hyaluronic acid gel injection was not significantly effective for knee osteoarthritis, but had less side effects than steroid injection.
3：Platelet rich plasma injection
Plasma is a liquid component of blood, while platelets are blood cells, which can promote blood coagulation and wound healing. Platelet rich plasma (PRP) contains more platelets.
The existing research results on the effect of PRP on moderate to severe pain are different. Some studies have found that it has no effect (Rf: 4). Some studies have shown that it can relieve pain (Rf: 5). PRP has a good effect on patients with mild OA symptoms, but the data is not sufficient. In addition, insurance generally does not pay for the treatment lacking sufficient evidence to support it.
4：Autologous serum injection
Autologous serum comes from its own blood and contains rich anti-inflammatory ingredients. This therapy has not been approved by FDA, but some studies have confirmed that it can benefit patients with knee osteoarthritis (Rf: 6). Due to limited evidence, clinicians do not recommend it, and the price of this therapy is higher than PRP.
5：Stem cell injection
The new cells and tissues of the human body come from stem cells, so stem cells are expected to rebuild joints. However, for the existing research (Rf: 7), it is necessary to confirm whether it is effective and safe for OA. Stem cell injection is more complex, demanding and requires more research. And the risk is even greater. FDA also warned about the related safety (Rf: 8).
As an invasive treatment, intra-articular injection also has side effects:
▷Infected
▷Hemorrhage
▷Pain
At the current stage, steroid injection is the only clinically recommended joint cavity injection therapy. Other injection methods are not the best at the current stage due to insufficient evidence support. Some studies have shown (Rf: 9) that injection of normal saline can also relieve pain (placebo effect), so more data are needed to support which injection method has clinical benefits.
Reference：
1. https://pubmed.ncbi.nlm.nih.gov/35383651/
2. 2019 American College of Rheumatology/Arthritis Foundation Guideline for the Management of Osteoarthritis of the Hand, Hip, and Knee
3. https://pubmed.ncbi.nlm.nih.gov/22868835/
4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8611484/
5. https://pubmed.ncbi.nlm.nih.gov/26432430/
6. https://pubmed.ncbi.nlm.nih.gov/25599270/
7. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7868850/
8. https://www.fda.gov/consumers/consumer-updates/fda-warns-about-stem-cell-therapies
9. https://pubmed.ncbi.nlm.nih.gov/28027657/
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