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Knee injections provide pain relief to patients with arthritis

Peter Hardcastle Article Knee Injections Final

Knee injections can offer relief from pain and inflammation in certain patients with arthritis. These patients present with inflammation, pain, cartilage damage, stiffness, and swelling. The injections are useful to break the cycle of pain and inflammation, improve knee function and overall quality of life.

Despite experiencing all these symptoms, a patient’s X-rays might show minimal damage in the knee. If our usual recommendations to lose weight, do certain types of exercise, modify activities, and use topical, pain killer or non-steroidal anti-inflammatories, don’t show results, then they may be a candidate for injections. This also buys time for patients who are too young to undergo a knee replacement.

We consider two types of patients for knee injections. The first is younger than 60, with early or mild arthritic symptoms. The second is an elderly person with severe arthritic symptoms, who isn’t a candidate for knee surgery. Before we can offer our patients a knee injection, we first need to exclude other possible causes of pain, such as the hip, back or meniscus. Patients’ whose X-rays show severe damage will probably need knee replacement surgery as a matter of time, regardless of whether they have symptoms or not.

At my practise we offer three types of knee injections namely, corticosteroid, hyaluronic acid, and plasma rich platelet injections. Each works in a different way and their safety and efficacy varies.

Corticosteroid injections

We use corticosteroid injections to provide short-term relief, predominantly in older patients who have moderate to severe pain.


  • Corticosteroid injections provide near immediate, short-term relief to patients experiencing moderate to severe pain as well as inflammation, stiffness, joint swelling, and effusion (fluid build-up).
  • We can sometimes use this injection to confirm a diagnosis.
  • Patients who need to be pain-free for a short-period of time, for example, for a sedentary holiday, may benefit from a corticosteroid injection.


  • The length of time that this injection provides relief for is unpredictable. It may be effective for a mere four weeks (Ayhan et al., 2014), although some of my patients have reported between four to six months of relief.
  • An increased risk of infection has been reported in patients who receive knee arthroplasty (replacement) or other major surgery within three months of receiving this injection.
  • It can accelerate cartilage degradation.
  • Cortisone is immunosuppressive. A patient can’t have the corticosteroid injection too soon before or after their Covid-19 vaccination, as it may supress the immune system’s response to the vaccine.
  • Some patients report that their knee feels loose and unstable after receiving the injection.
  • Some patients will experience a steroid flare between 6 – 12 hours after the injection was administered. This will resolve within one to three days, after which the pain-relief function of the injection will be felt.

Hyaluronic acid

A hyaluronic acid injection helps to recreate the lubricating, cushioning effect of the synovial (joint) fluid in the knee. The arthritic knee will need to be aspirated before administering the injection to remove the old, inflammatory mediators that are present. I usually use this injection on my older patients, from around 60 years of age and above. Patients who received relief from this injection can get repeat injection/s by six months.


  • Hyaluronic acid provides lubrication in the knee which helps during slow joint movements and acts as shock absorber during rapid joint movements. It reduces stress and friction on cartilage (Ayhan et al., 2014).
  • The hyaluronic acid injection has analgesic (pain relief) and anti-inflammatory properties.
  • This injection can provide relief for around six months.
  • These injections are safer than repeated corticosteroid injections (Fusco et al., 2021).
  • The hyaluronic acid injection can be combined with a corticosteroid injection to ensure that the patient benefits from their long and short-term effectiveness respectively.


  • This injection is relatively expensive and medical aids don’t cover the cost of it.
  • The injection takes around four weeks to take effect.
  • Unfortunately, the efficacy of this injection is unpredictable. I have had patients who have not experienced any relief from it.

Platelet Rich Plasma (PRP)

The Platelet Rich Plasma (PRP) injection consists of blood which we draw from the patient in question. We spin the blood once in a centrifuge, which according to Ayhan et al. (2014) results in a “highly concentrated sample of platelets, which is four to five times higher than that of normal blood”. The platelets are degranulated to release growth factors.

When injected, these platelets “release biologically active protein that… promote tissue healing” (Fusco et al., 2021). The growth factors give the cartilage cells a ‘kick-start’ of sorts to stabilise and repair itself.

PRP is the first of the three injections that I would offer to a younger patient, around the age of 40.


  • The PRP injection is effective up to eight months
  • PRP reduces inflammation, relieves pain, improves function and may help with cartilage regeneration (Ayhan et al., 2014).
  • This injection is relatively low cost.
  • The PRP injection is safe.
  • The most promising results are in younger patients and those with mild arthritis.


  • It takes four to five weeks before the effects of the injection can be felt.
  • A patient may need a second or third injection before feeling any benefits.
  • Ayhan et al. point out that there’s no substantive data confirming that cartilage and meniscus will regenerate in patients who have substantial and irreversible bone and cartilage damage.

If you experience pain, swelling or both in your knee, please consult an orthopaedic specialist for an examination. Your specialist will determine the cause of your symptoms and recommend a treatment plan that is specific to you.


Ayhan A, Kesmezacar H, Akgun I. Intraarticular injections (corticosteroid, hyaluronic acid, platelet rich plasma for the knee osteoarthritis. World Journal of Orthopedics. 18 July 2014; 5(3): 351 – 361. DOI: doi:10.5312/wjo.v5.i3.351

Fusco G, Gambaro FM, Di Matteo B, Kon E. Injections in the osteoarthritic knee: a review of current treatment options. EFORT Open Reviews. June 2021. DOI: 10.1302/2058-5241.6.210026

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