The influence of age on weight-bearing joint reposition sense of the knee

Knee joint-position sensitivity has been shown to decline with increasing a ge, with much of the research reported in the literature investigating this age effect in non-weight-bearing (NWB) conditions. However, little data is available in the more functional position of weight-bearing conditions. Th e objective of this study was to identify the influence of age on the accur acy and nature of knee joint-position sense (JPS) in both full weight-beari ng (FWB) and partial weight-bearing (PWB) conditions and to determine the e ffect of lower-extremity dominance on knee JPS. Sixty healthy subjects from three age groups (young: 20-35 years old, middle-aged: 40-55 years, and ol der: 60-75 years) were assessed. Tests were conducted on both the right and left legs to examine the ability of subjects to correctly reproduce knee a ngles in an active criterion-active repositioning paradigm. Knee angles wer e measured in degrees using an electromagnetic tracking device, Polhemus 3S pace Fastrak, that detected positions of sensors placed on the test limb. E rrors in FWB knee joint repositioning did not increase with age, but signif icant age-related increases in knee joint-repositioning error were found in PWB. It was found that elderly subjects tended to overshoot the criterion angle more often than subjects from the young and middle-aged groups. Subje cts in all three age groups performed better in FWB than in PWB. Difference s between the stance-dominant (STD) and skill-dominant (SKD) legs did not r each significance. Results demonstrated that for, normal pain-free individu als, there is no age-related decline in knee JPS in FWB, although an age ef fect does exist in PWB. This outcome challenges the current view that a gen eralised decline in knee joint proprioception occurs with age. In addition, lower-limb dominance is not a factor in acuity of knee JPS.