From the Guidelines
For PRP (Platelet-Rich Plasma) injections of the knee, the primary structures targeted include the knee joint space, specifically the tibiofemoral joint compartment, and sometimes the patellofemoral joint. The injection is typically delivered into the intra-articular space of the knee, where the concentrated platelets can release growth factors to promote healing of damaged cartilage, ligaments, tendons, muscles, and bones. In some cases, specific structures such as the medial or lateral meniscus, anterior cruciate ligament (ACL), or areas of cartilage damage may be targeted more precisely using ultrasound or fluoroscopic guidance. However, it is essential to note that the current evidence does not strongly support the use of PRP for knee OA, as stated in the 2020 American College of Rheumatology guideline, which strongly recommends against platelet-rich plasma treatment in patients with knee and/or hip OA 1. The procedure involves first harvesting blood from the patient, processing it in a centrifuge to concentrate the platelets, and then injecting this concentrated solution into the knee using aseptic technique. A local anesthetic like lidocaine may be administered prior to the PRP injection to minimize discomfort. Patients should avoid anti-inflammatory medications for at least 2 weeks before and after the procedure, as these can interfere with the inflammatory cascade necessary for PRP's healing effects. Following injection, patients typically need to limit weight-bearing activities for 24-48 hours and gradually return to normal activities over 1-2 weeks. It is crucial to consider the lack of standardization in available preparations of platelet-rich plasma and techniques used, as highlighted in the 2020 guideline 1. Additionally, the evidence review from the 2021 study found mixed results regarding the use of PRP in the treatment of knee OA, with some studies reporting no benefit and others reporting small benefits 1.
Key Considerations
- The knee joint space, specifically the tibiofemoral joint compartment, and sometimes the patellofemoral joint are the primary structures targeted for PRP injections.
- The use of PRP for knee OA is not strongly supported by current evidence, with the 2020 American College of Rheumatology guideline strongly recommending against it 1.
- The procedure involves harvesting blood, processing it in a centrifuge, and injecting the concentrated platelets into the knee using aseptic technique.
- Patients should avoid anti-inflammatory medications and limit weight-bearing activities after the procedure.
- The lack of standardization in available preparations of platelet-rich plasma and techniques used is a significant concern, as highlighted in the 2020 guideline 1.
Structures Targeted
- Knee joint space
- Tibiofemoral joint compartment
- Patellofemoral joint
- Medial or lateral meniscus
- Anterior cruciate ligament (ACL)
- Areas of cartilage damage
Procedure
- Harvesting blood from the patient
- Processing it in a centrifuge to concentrate the platelets
- Injecting the concentrated solution into the knee using aseptic technique
- Administering a local anesthetic like lidocaine to minimize discomfort
- Avoiding anti-inflammatory medications for at least 2 weeks before and after the procedure
- Limiting weight-bearing activities for 24-48 hours and gradually returning to normal activities over 1-2 weeks.
From the Research
Structures Injected for Platelet-rich Plasma (PRP) Therapy of the Knee
The structures injected for PRP therapy of the knee include:
- Intra-articular space, as indicated by studies 2, 3, 4, 5, 6
- Knee joint, as mentioned in studies 2, 3, 5, 6
- Medial collateral ligament (MCL), as specified in study 4
Injection Procedure
The injection procedure for PRP therapy of the knee involves:
- Ultrasound-guided knee injection, as described in study 2
- Intra-articular injection of autologous PRP, as mentioned in studies 3, 4, 5, 6
- Injection of PRP solution, typically 3-7 mL, as specified in studies 2, 5
Treatment Outcomes
The treatment outcomes for PRP therapy of the knee include: