PRP

No guideline sets a safe number. The one randomized trial that tested four a year in the knee found more cartilage loss than saline and no better pain relief. A 2024 review found guidelines on how often, how long and how many lifetime corticosteroid injections are safe still lacking.

To find a PRP doctor who follows published research protocols, ask the clinic to walk you through its protocol step by step and name the paper behind each step: the platelet dose, the preparation, who places the needle and under what imaging, how a second injection is decided, the rehab and how results are followed.

Orthobiologics are biologic injections, most often prepared from your own blood, bone marrow or fat, used for joint, tendon and ligament pain. They fall into two families: blood-based platelet-rich plasma (PRP), and tissue- or cell-based products such as bone marrow aspirate (BMA) and fat-derived microfragmented adipose tissue (MFAT).

There is no single number: in early to moderate knee arthritis, trials found two or three injections beat one at six to twelve months, while in one review most ultrasound-guided tendon trials used one injection, and reviews disagree on how much it helps. The better answer is the number that gets you back, and it depends on the tissue, the stage and the dose in each syringe.

PRP works for some conditions and not others, and the trials and reviews we read show which. The evidence is most favorable in knee arthritis, where an 18-trial meta-analysis found PRP better than placebo, though one large saline-controlled trial did not.

For knee arthritis, the research points to a dose in the billions: PRP arms with positive results averaged about 5.5 billion platelets per injection, and one meta-analysis puts the threshold above 10 billion. Arms without benefit averaged about 2.3 billion. A ‘times baseline’ figure describes concentration; the dose reviews count platelets.

There is almost no downtime after a PRP injection, but that is not the same as being better. Most people walk out, drive themselves home, and return to desk work the same day or the next. What takes time is healing, not recovery: expect a sore flare for the first few days, easing through weeks one and two, with meaningful tissue change over roughly six to twelve weeks.

For mild to moderate knee arthritis, cortisone works faster and PRP tends to last longer. Cortisone is an anti-inflammatory, so relief usually arrives within days. PRP starts a repair response, so it takes weeks to build. In a 2021 meta-analysis of randomized trials, PRP beat cortisone on pain, stiffness and function at three, six and nine months, with the largest gap at six and nine.

The main side effect of a PRP injection is a sore joint or tendon for a few days, and that soreness is expected rather than a complication. PRP is autologous, made from a sample of your own blood, so allergic reaction and rejection are not on the list of things that can go wrong.

PRP can help a partial rotator cuff tear or a painful, degenerating tendon. It cannot reattach a tendon that has torn all the way through, or a labrum that has pulled away from the bone. Those are mechanical problems, and an injection does not sew anything back together.