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Utilisation of joint movement range in arboreal primates compared with human subjects: an evolutionary frame for
1Department of Anatomy with Radiology, School of Medicine, University of Auckland, New Zealand.
Objective:
To determine whether an arboreal lifestyle required full use of movement ranges underutilised in nine joint groups in humans, because under-utilisation of available movement range may be associated with susceptibility to primary osteoarthritis.
Methods:
Utilisation of the nine joint groups was studied in two species of primate exercising in a simulated arboreal environment, using 'focal animal' observation techniques supplemented by telephoto photography and by review of archival material from other sources. Fifteen apes were observed over a total observation period of 20.2 man-hours and 152 films were analysed for utilisation of movement range.
Results:
With one exception, all the movement ranges reported to be under-utilised in humans were fully utilised by the apes in climbing activities. The exception, metacarpophalangeal extension, was an essential component of the chimpanzee ground progression mode of knuckle walking.
Conclusions:
The underused movement range in several human joints is explicable as residual capacity from a semiarboreal lifestyle. If the correlation with primary osteoarthritis is confirmed, it suggests that the disease may reflect a disparity between inherited capacity and current need. The significance of the result lies in its implication that primary osteoarthritis may be preventable.