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Since we introduced cellular therapeutics for orthopedic problems like knee arthritis to the US in 2006, many studies from other authors have confirmed the safety and efficacy of the easy-to-perform office procedures.  By now, most orthopedic clinics across the country, but particularly in Florida, Texas and California have jumped on board with this treatment modality given the fact that it serves a patient population that would otherwise require total knee replacement and expose patients to potentially avoidable complications.  French orthopedic surgeon Philippe Hernigou introduced the techniques 25 years ago and his most recent work has confirmed improvement both clinically and on imaging studies examining subchondral bone recovery and cartilage recovery. 

Knee joint arthritis must be considered a whole-joint disease and is primarily a disease of the (subchondral) bone beneath the cartilage covering of the bone ends.  Arthritis does not progress in the human or any animal model until the subchondral bone stiffens and loses its impact elasticity.  Stiffening of the subchondral bone is the rate limiting step and leads to breakdown of the cartilage matrix and the cells that are contained within the matrix they make.

Initially, the load that is typically absorbed by subchondral bone exceeds the loading capacity of the protein cadherin and integrin protein networks connecting cells to each other and to their matrix.  These signals are amplified through signaling mechanisms causing activation of bone remodeling cells that stiffen the bone underlying the cartilage, directed by gravitational loads.  This remodeling is an adaptive response to loads at impact.  However, once the subchondral bone reaches its maximum stiffness, the loads are transferred directly to the cartilage matrix and cells that are unable to withstand the impact and disintegrate with matrix destruction.   

Young’s ‘modulus of elasticity’ in the subchondral bone is compromised and causes predictable progression in a stepwise fashion beginning on the concave side of the joint (tibia) to the convex side of the joint (femur).  Ultimately, the soft cartilage begins to fragment into the joint fluid, followed by exposed cell lysis that causes an exuberant inflammatory response generated by inflammatory cells of the knee joint lining that make up approximately 20 percent of the cell mass.  Addressing the problem with the subchondral bone has emerged as likely more important than routine joint injections with marrow concentrates in terms of efficacy.  The procedure is still performed in the office setting under local anesthetic and recovery is prompt.

Recently, several authors have concluded that previously performed cell therapy procedures were not adequate because they did not address the stiff bone that underlies diseased cartilage.  Other authors have noted that the ‘new standard’ for orthopedic marrow therapy in the setting of knee arthritis is stimulation of the subchondral bone by decompression and marrow exchange in combination with the intra-articular approach.  Most authors agree that the mechanism of action of the intra-articular component of the procedure is a shift from catabolic to anabolic conditions, effected by transplantation of cells, growth factors and other anabolic, anti-inflammatory proteins.  That’s why so many research labs are working on drugs and smart molecules that target these protein molecules.  However, it may be that recovery of the subchondral bone in the setting of knee arthritis is an even more important mechanism of pain relief as Doctor Hernigou has suggested.  Other important adjuncts include the awareness of and attention to mechanical axis deviation, dietary supplementation and inclusion of low intensity pulsed ultrasound (LIPUS) in the algorithm.  Sherman Austin Yeargan, III, MD completed his undergraduate degree in chemistry at UNC-Chapel Hill and his MD at the ECU Brody School of Medicine. His next 7 years included an orthopedic surgery residency and a research fellowship at the University of Hawaii followed by a shoulder, elbow, knee and sports medicine fellowship at the Steadman-Hawkins Clinic in Vail, Colorado. He now focuses on non-operative orthopedic treatments at the Regenerative Medicine Clinic.