Effects of experimentally-induced anterior knee pain on knee joint position sense in healthy individuals.

PURPOSE The ability to sense the position of limb segments is a highly specialised proprioceptive function important for control of movement. Abnormal knee proprioception has been found in association with several musculoskeletal pathologies but whether nociceptive stimulation can produce these proprioceptive changes is unclear. This study evaluated the effect of experimentally induced knee pain on knee joint position sense (JPS) in healthy individuals. STUDY DESIGN Repeated measures, within-subject design. METHODS Knee JPS was tested in 16 individuals with no history of knee pathology under three experimental conditions: baseline control, a distraction task and knee pain induced by injection of hypertonic saline into the infrapatellar fat pad. Knee JPS was measured using active ipsilateral limb matching responses at 20 degrees and 60 degrees flexion whilst non-weightbearing (NWB) and 20 degrees flexion single leg stance. During the tasks, the subjective perception of distraction and severity of pain were measured using 11-point numerical rating scales. RESULTS Knee JPS was not altered by acute knee pain in any of the positions tested. The distraction task resulted in poorer concentration, greater JPS absolute errors at 20 degrees NWB, and greater variability in errors during the WB tests. There were no significant correlations between levels of pain and changes in JPS errors. Changes in JPS with pain and distraction were inversely related to baseline knee JPS variable error in all test positions (r=-0.56 to -0.91) but less related to baseline absolute error. CONCLUSION Knee JPS is reduced by an attention-demanding task but not by experimentally induced pain.