Interestingly, the patients with intact but fibrillated cartilage did NOT show evidence of repair. This report supports the premise of the cartilaginous aggregates being the source of repair when a joint with eburnated bone is unloaded as with osteotomy.
Lanny L Johnson, Christopher Verioti, Jonathan Gelber, Myron Spector, Darryl D’Lima, Andrew Pittsley. The pathology of the end-stage osteoarthritic lesion of the knee: Potential role in cartilage repair. The Knee. 8 (6) 2010: 402-406.
This publication shows the cartilagenous aggregates near and on the surface as a potential for cartilage regeneration. In addition, surface pits have been reported for the first time. These pits may serve as a “home” for various therapeutics.
Two recent publications further the evidence of the sole importance of unloading the joint.
Jung WH, Takeuchi R, Chun CW, Lee JS, Ha JH, Kim JH, Jeong JH. Second-look arthroscopic assessment of cartilage regeneration after medial opening-wedge high tibial osteotomy. Arthroscopy. 2014 Jan;30(1):72-9. doi: 10.1016/j.arthro.2013.10.008.
They concluded that “The degenerated cartilage of the medial femoral condyle and medial tibial plateau could be partially or entirely covered by newly regenerated cartilage at 2 years after adequate correction of varus deformity by medial opening-wedge high tibial osteotomy without cartilage regeneration strategies.”
Hinterwimmer S, Jaeger A, von Eisenhart-Rthe R, Vogl T, Graichen H. Paper 47: Cartilage Morphology after High Tibial Osteotomy for Varus Gonarthrosis. Arthroscopy. 2012. 28 (9); e368-362.
They concluded “The preoperative medial (tibial) cartilage loss may be assessed as an expression of the increased mechanical loading in varus malalignment. The valgus-producing opening wedge HTO halted cartilage loss in the medial compartment or achieved stabilisation of the cartilage morphology. The correction of the mechanical axis into the lateral compartment led to no cartilage loss there either. The cartilage in the lateral compartment appears to be able to withstand this increased mechanical load. The results presented in this paper support clinical long-term studies already mentioned above and lead to an improved understanding of the processes taking place in the knee joint following valgus-producing HTO. These results must be followed over time.”
Summary: It is clear from the medical literature that reduction of abnormally high forces across the most severe arthritic joint will result in repair of the joint by regrowth of articular cartilage. It is likely the normal healing process is based upon the proliferation of the cartilaginous aggregates present on the surface of the most severe arthritic condition.