Comparison of proprioception in arthritic and age-matched normal knees.

BACKGROUND Proprioception--one's ability to sense joint position and joint motion--is affected by factors such as age, muscle fatigue, and osteoarthritis. Most proprioception studies have focused on young active subjects or on recipients of total knee replacements. Few have involved a population with arthritic knees prior to total knee replacement or persons similar in age to patients with advanced knee arthritis who are to have total knee arthroplasty. The purpose of the present study was to determine (1) if proprioception in arthritic knees differs from proprioception in nonarthritic, age-matched, normal knees; (2) if, when proprioception in one knee is reduced by the presence of advanced gonarthrosis, it also is reduced in the contralateral knee irrespective of the presence of arthritis; and (3) if a person's grade of arthritis is associated with his or her level of proprioception. METHODS This study compared the proprioception levels of a group of 117 patients who were scheduled for total knee arthroplasty because of severe arthritis (mean age, 67.9 years) with those of a control group of forty patients who were recruited from a hospital-based cardiac rehabilitation program and did not have knee arthritis (mean age, 68.3 years). We used a customized Biodex System 2 Multi-Joint Testing and Rehabilitation System to compare proprioception (the threshold to detection of passive motion) between the two groups. RESULTS Middle-aged and elderly persons with advanced knee arthritis were significantly less able to detect passive motion of the knee than were middle-aged and elderly persons without knee arthritis. Patients who had arthritis in only one knee had a reduced ability to detect passive motion of both knees. There was no significant association between the radiographic severity of arthritis and the threshold to detection of passive motion in patients with advanced knee arthritis. CONCLUSIONS Knee proprioception in middle-aged and elderly persons with advanced knee arthritis is reduced in comparison with that in middle-aged and elderly persons without arthritis. Such loss of proprioception is independent of the severity of knee arthritis and may foretell the development of arthritis. When a patient has reduced proprioception with regard to one knee affected by arthritis, he or she also has reduced proprioception with regard to the contralateral knee, independent of the presence or severity of degenerative arthritis. When an investigator is evaluating changes in proprioception after knee arthroplasty, it is best to compare the knee with the patient's untreated knee rather than with age-matched controls.