Platelet-Rich Plasma (PRP) therapy for the knee is a regenerative treatment that uses a concentration of a patient’s own platelets to stimulate healing in damaged tissue. Unlike a steroid injection, which provides rapid but temporary pain relief by suppressing inflammation, PRP works by triggering a controlled inflammatory response to initiate long-term repair. This distinction means the post-injection experience is fundamentally different, requiring patience and specific aftercare to maximize the body’s natural healing cascade. Understanding the phased recovery process is paramount to achieving a successful outcome.
Immediate Post-Injection Care and Restrictions
The first 48 to 72 hours following the injection represent the acute inflammatory phase, which is a necessary part of the healing process. Patients should expect a temporary increase in discomfort, including soreness, mild swelling, and warmth around the injection site, as the concentrated platelets release growth factors and signal the body to begin repair.
The most important restriction during this period involves medication management, specifically the strict avoidance of Non-Steroidal Anti-Inflammatory Drugs (NSAIDs), such as ibuprofen, naproxen, and aspirin. NSAIDs inhibit the enzymes crucial for platelet function and the release of healing growth factors, directly counteracting the regenerative mechanism of PRP. To manage the expected pain, acetaminophen (paracetamol) is generally recommended as it does not interfere with platelet activity.
Activity must be significantly limited in the first few days, focusing on relative rest and avoiding strenuous activities or high-impact loading on the knee joint. While complete immobilization is not advised, patients should limit walking to short distances and follow any specific instructions regarding partial weight-bearing. Avoiding hot baths, saunas, and excessive heat exposure is also advised, and some protocols suggest avoiding ice application for the first 48 to 72 hours to allow the initial inflammatory cascade to proceed unimpeded.
Recovery Timeline and Activity Progression
The transition from the acute phase marks the beginning of the sub-acute and rehabilitation phases, which typically span the first six weeks post-injection. By the end of the first week, the initial soreness and swelling should be substantially reduced, allowing for a gradual reintroduction of gentle movement. Light walking and simple, non-strenuous daily activities can be resumed, as movement helps promote circulation and prevent joint stiffness.
The focus in the subsequent weeks is on a structured, slow progression of activity rather than an immediate return to pre-injury exercise. Formalized physical therapy (PT) often begins between the second and sixth week, depending on the specific protocol and the patient’s response. This structured rehabilitation helps strengthen the muscles surrounding the knee joint and maximize the effect of the PRP.
Physical therapy activities initially center on restoring range of motion and improving muscle activation without placing excessive stress on the healing tissues. As the knee tolerates more load, the exercises will progress to include low-impact conditioning, such as stationary cycling or swimming. High-impact activities like running or jumping remain restricted. Adherence to this gradual plan is paramount, as overloading the joint too early can disrupt the tissue remodeling process initiated by the PRP.
When Therapeutic Improvement is Expected
It is important to set realistic expectations, as PRP is a regenerative treatment, not an immediate pain reliever like a corticosteroid injection. The goal of the therapy is to stimulate biological repair, a process that requires time for new, stronger tissue to form. Therefore, patients should not anticipate immediate symptomatic relief in the days or first few weeks following the procedure.
Initial signs of therapeutic benefit, such as a noticeable reduction in pain or improved function, typically begin to emerge between four and eight weeks post-injection. This timeframe corresponds with the body’s shift from the proliferative phase to the remodeling phase of healing. The full, peak results of the PRP treatment are often not experienced until three to six months after the procedure.
In cases where the initial response is insufficient after several months, a provider may discuss the possibility of a repeat injection. The long-term success of the treatment is measured by sustained improvement in pain and function, which can last for a year or longer. The slow, gradual nature of this improvement contrasts sharply with the quick, but temporary, relief provided by other injection types.
Recognizing Complications and Warning Signs
While PRP is considered a safe procedure because it uses the patient’s own blood, it is necessary to monitor for signs that differentiate expected post-injection soreness from a true complication. Mild pain, redness, and swelling that occur immediately after the injection and resolve within 72 hours are normal parts of the inflammatory healing response. However, certain symptoms require immediate contact with a healthcare provider for evaluation:
- Fever, or severe and rapidly worsening knee pain that does not improve after the third day.
- Significant, spreading redness and warmth at the injection site, indicating a possible infection.
- Persistent numbness, tingling, or a foot drop, which could indicate irritation or injury to a nearby nerve structure.
- Symptoms of a severe allergic reaction, such as difficulty breathing or widespread rash (although rare).