What are infiltrations?

Infiltration is a procedure through which the doctor injects a drug or biological product into a joint, the synovial sheaths of the tendons, the periarticular bursa, the spinal nerve roots or other structures, with the aim of the product acting on that area.

In some joints, such as the hip and possibly the knee and shoulder, it is recommended that infiltrations be performed under ultrasound guidance, since this increases the effectiveness of the procedure.

To perform the infiltration, the area must be sterilized to reduce the possibility of infection.

For these reasons, among others, it is of the utmost importance that this procedure always be performed by a professional with suitable experience and knowledge.

What is the purpose of an infiltration?

The main objective is to reduce inflammation, achieving greater comfort of the patient and, in some cases, delaying the need for surgery.

Infiltrations are indicated in cases of inflammatory disease, joint effusions, tendinitis, osteoarthritis or in sports-related muscle injuries, among others.

 Are there different types of effusions?

Specifically for the knee, and at an intraarticular level, the content of the infiltration can vary depending on the injury. The main solutions are:

  1. Hyaluronic acid
  2. Platelet-rich plasma
  3. Mesenchymal cells (stem cells)
  4. Corticosteroids

Hyaluronic acid

Hyaluronic acid is a natural component of the human body that is found in particular in the joints, skin and vitreous humor.

Joints have synovial fluid, whose primary component is hyaluronic acid. This synovial fluid has viscoelastic characteristics that lead it to participate in homeostasis, that is, that maintain their stable internal conditions, generating a “lubricating” effect and acting as a natural “shock absorber” against impacts.

Due to the progressive accumulation of sports activities and the joint’s own degenerative processes, the components of the synovial fluid begin to change, affecting the functions of the hyaluronic acid.

To respond to this condition, intraarticular infiltration of hyaluronic acid has been a possibility for years. These have progressed to the point that, currently, it is no longer necessary to repeat them every 2 or 3 weeks as in the past; instead, a single infiltration can be done, thanks to the development of high-molecular-weight drugs which, for the most part, are very effective and well tolerated.

Infiltration of hyaluronic acid aims to act as a potent local anti-inflammatory, which goes directly to the joint to reestablish the viscoelastic properties of the synovial fluid, keeping the homeostasis of the knee in optimal conditions.

A low percentage of patients experience swelling/joint pain in the first 24/48 hours after the infiltration; use of ice and relative rest during this period is therefore recommended.

Platelet-Rich Plasma (also called “Growth factors”)

After collecting the patient’s blood and subjecting it to a specific centrifuge process, the so-called platelet-rich plasma (PRP) is obtained. This has been shown to have a potent local inflammatory effect, at both the myotendinous and joint level. These effects are motivated by “growth factors,” which are substances that act by inhibiting the proinflammatory cytokines that participate in the mechanisms that trigger pain.

Despite the good results obtained with this technique in terms of inflammatory control in knees with excessive sports-related demands or patients with early degenerative processes, there is no clear scientific evidence that demonstrate repair and/or regeneration at the joint through the use of this practice.

Mesenchymal cells

Also known as “stem cells.” Today, there is a great discrepancy of opinion regarding their use and indications.

They are cells derived from the mesoderm (one of the three primary germ layers that make up the embryo), which have pluripotent differentiation, that is, they have the ability to differentiate into different types of cells.

Currently, and based on the existing scientific evidence, it can be concluded that they exert their effect through a potent anti-inflammatory action.

In daily practice, we believe it is logical and prudent to be very clear with patients about the expectations of this type of treatment, based on the existing scientific evidence, and thus avoid failures based on expectations that are often too high.


They act as potent anti-inflammatory agents and can be infiltrated along with anesthetics.

It is currently one of the most-used drugs for performing intraarticular infiltrations. However, it is not the first choice at Equilae, due to the undesirable effects that can occur in the joint over time.