Osteoarthritis of the Knee: PRP or Hyaluronic Acid - Which Option is Better?
Introduction
This article is a translation of the study from the Official Journal of Malaysian Orthopaedic Association and ASEAN Orthopaedic Association.
Knee osteoarthritis is the most common form of chronic arthritis. It causes severe pain, disability, loss of function, and affects the quality of life of patients.
Studies have shown that 15% of the global population suffers from osteoarthritis, with 39 million people in European countries and more than 20 million Americans affected.
Knee osteoarthritis
Knee osteoarthritis is characterized by a degeneration of the joint cartilage, eventually leading to joint destruction.
The underlying causes of osteoarthritis are multifactorial and involve several predisposing factors such as mechanical injuries, obesity, genetic factors, inflammatory joint diseases, previous joint infections, advanced age, metabolic factors, osteoporosis, and ligament laxity.
Osteoarthritis is diagnosed through clinical evaluation and additional radiological examination. Less than 50% of patients with radiological changes of osteoarthritis are symptomatic; therefore, treatment is based on symptoms rather than radiological changes.
The main treatments for early-stage knee osteoarthritis include pain relievers, activity modification, and physiotherapy.
Over time, patients typically become refractory to the initial treatment regimen, and reconstructive surgery becomes the next treatment modality.
Commonly used pain relievers in patients with knee osteoarthritis only reduce inflammation and pain but are ineffective in slowing the progression of the disease.
Studies conducted
Contemporary studies conducted in developed countries have demonstrated the utility of platelet-rich plasma (PRP) in the treatment of knee osteoarthritis.
PRP is a platelet concentrate (2 to 10 times the baseline concentration) obtained from an autologous patient blood sample through centrifugation. Platelets store over 1500 active proteins in alpha and dense granules.
Alpha granules contain numerous growth factors (GF) such as Platelet-Derived Growth Factor (PDGF), Transforming Growth Factor-beta (TGF-β), Vascular Endothelial Growth Factor (VEGF), Insulin-Like Growth Factor-1 (IGF-1), Fibroblast Growth Factor (FGF), and Epidermal Growth Factor (EGF) that promote the healing potential of degenerated joint cartilage.
Furthermore, dense granules contain adenosine diphosphate, adenosine triphosphate, calcium, histamine, serotonin, and dopamine, which contribute to the regeneration of degenerated tissues.
Studies have suggested that the use of platelet-rich growth factor plasma improves the regeneration of articular cartilage.
The objective of this study is to analyze the effectiveness of intra-articular PRP injection compared to HA injection in patients suffering from grade III and IV knee osteoarthritis.
This study should significantly contribute to improving the quality of life of patients with severe knee osteoarthritis who are not suitable for surgery, do not wish to undergo surgical intervention, or have limited financial means.
Methodology
This was a cross-sectional study with a retrospective review of medical records conducted from October 2013 to April 2014 at the Malacca General Hospital and was approved by the hospital's ethics committee and the National Clinical Research Centre.
Data were collected and reviewed from the knee intra-articular injection registry. In total, 254 patients had received a knee intra-articular injection between October 2013 and March 2014.
Among the 254 patients, 70 had knee osteoarthritis of grade III or IV (primary osteoarthritis).
Patients with knee osteoarthritis of grade I and II, secondary knee osteoarthritis, patients who received HA injection with concentrations and molecular weights other than those mentioned in the inclusion criteria, patients with osteoarthritis in other joints, those suffering from other inflammatory and non-inflammatory joint diseases, coagulopathies, and local or systemic infections were excluded from this study.
Sixty-four patients (101 knees) who met the criteria were selected, and six patients were excluded based on exclusion criteria. The study group included 24 men and 40 women, with an average age of 66 years (range 50 - 87).
A total of 101 knees had received intra-articular injections:
- 37 patients with bilateral injections (74 knees) and 27 patients with unilateral injections. Among these, 56 knees had received autologous intra-articular PRP injections, while 45 knees had HA injections.
Knee assessment and pain scores were systematically recorded and documented at the Malacca center, using the International Knee Documentation Committee (IKDC) questionnaires and the Visual Analog Scale (VAS) before the injections, and after two months and six months following the injection. IKDC was preferred over other measurement tools like the Knee Injury and Osteoarthritis Outcome Score (KOOS) and the Western Ontario and McMaster Universities Arthritis Index (WOMAC) due to its high reliability and validity.
All patients included in the study received 4 ml of high molecular weight hyaluronic acid (average 1,476 x 106 Daltons) with a concentration of 22mg/ml. High molecular weight HA was specifically chosen because previous studies have shown greater and longer-lasting effectiveness in reducing pain and other symptoms and in joint function recovery compared to low molecular weight HA (LMW-HA).
PRP injections are prepared by taking 30 ml of the patient's venous blood, mixed with an anticoagulant, and centrifuged using the duo-spin method, at a speed of 2500 rpm for the first 5 minutes and then at 3200 rpm for the next 10 minutes (15 minutes in total).
Three distinct layers are produced at the end of centrifugation:
- plasma, the leukocyte layer (platelets), and red blood cells. Ninety-five percent of the plasma layer is discarded, and the remaining layers are mixed, resulting in approximately 2.5 to 3 ml of PRP at the end of the process, with an average platelet concentration of 1.4 to 1.6 million/μl.
Results
Sixty-four patients were selected for the study based on our inclusion criteria as mentioned above.
Among them, 101 knees received an intra-articular injection (37 patients with bilateral knee injection and 27 patients with unilateral knee injection). Forty-seven knees were injected with HA, and 56 knees were injected with PRP.
As illustrated in the graph below, both groups of patients showed improvements in terms of functional status based on the IKDC scores.
Statistically significant improvements in IKDC scores were noted during the evaluation two months after the injection, with an average value of 7.0 in patients receiving HA and an average value of 16.4 in patients receiving PRP.
The improvement was more apparent during the evaluation six months after the injection, with an average value of 24.3 achieved in patients who received PRP, compared to an average value of 12.2 in patients who received HA, as shown in the table below.
Furthermore, progress was also evident on the VAS scale in terms of a decrease in pain intensity in both groups.
Results improved significantly in the long term, as better pain control was achieved during the six-month evaluation compared to the two-month evaluation in both groups.
During the six-month evaluation, the HA group showed improvement with an average pain score of 0.8.
On the other hand, the PRP group demonstrated a greater improvement in the pain score with an average score of 1.9, as shown in the following graph.
Conclusion
The study conducted by Malacca General Hospital strongly suggests that PRP injection is more effective than HA. Therefore, we recommend PRP as an optional treatment modality in the management of grade III and IV knee osteoarthritis in terms of functional outcomes and pain control for a duration of up to 6 months when surgical treatment is not an option.
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