Age when articular cartilage maturation occurs

Often we are asked at what age is it safe to begin training horses. Here is a study that examines articular cartilage during growth that has a somewhat surprising finding: adult properties of the cartilage develop between 5 and 11 months. Hmph, it seems awful early to begin serious training of horses and would urge caution using this data to begin significantly earlier training in earnest. There are other factors, such as time and quality of recovery following exercise not addressed. It does certainly support the idea that light training started early may not be deleterious to the long term health of the joints.
DrO

Sci Rep. 2018 Jul 27;8(1):11357.
Composition, structure and tensile biomechanical properties of equine articular cartilage during growth and maturation.
Oinas J1,2, Ronkainen AP3, Rieppo L1,2,4, Finnilä MAJ1,2,4, Iivarinen JT4,5, van Weeren PR6, Helminen HJ5, Brama PAJ7, Korhonen RK4, Saarakkala S1,2,8.

Author information:
1. Research Unit of Medical Imaging, Physics and Technology, Faculty of Medicine, University of Oulu, Oulu, Finland.
2. Medical Research Center, University of Oulu and Oulu University Hospital, Oulu, Finland.
3. Department of Applied Physics, University of Eastern Finland, Kuopio, Finland. ari.p.ronkainen@uef.fi.
4. Department of Applied Physics, University of Eastern Finland, Kuopio, Finland.
5. Institute of Biomedicine, University of Eastern Finland, Kuopio, Finland.
6. Department of Equine Sciences, University of Utrecht, Utrecht, Netherlands.
7. Veterinary Clinical Sciences, School of Veterinary Medicine, University College Dublin, Dublin, Ireland.
8. Department of Diagnostic Radiology, Oulu University Hospital, Oulu, Finland.
Abstract

Articular cartilage undergoes structural and biochemical changes during maturation, but the knowledge on how these changes relate to articular cartilage function at different stages of maturation is lacking. Equine articular cartilage samples of four different maturation levels (newborn, 5-month-old, 11-month-old and adult) were collected (N = 25). Biomechanical tensile testing, Fourier transform infrared microspectroscopy (FTIR-MS) and polarized light microscopy were used to study the tensile, biochemical and structural properties of articular cartilage, respectively. The tensile modulus was highest and the breaking energy lowest in the newborn group. The collagen and the proteoglycan contents increased with age. The collagen orientation developed with age into an arcade-like orientation. The collagen content, proteoglycan content, and collagen orientation were important predictors of the tensile modulus (p < 0.05 in multivariable regression) and correlated significantly also with the breaking energy (p < 0.05 in multivariable regression). Partial least squares regression analysis of FTIR-MS data provided accurate predictions for the tensile modulus (r = 0.79) and the breaking energy (r = 0.65). To conclude, the composition and structure of equine articular cartilage undergoes changes with depth that alter functional properties during maturation, with the typical properties of mature tissue reached at the age of 5-11 months.