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Knee replacement did not affect contralateral knee loading at early follow-up
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MANCHESTER — Patients with single joint knee osteoarthritis had abnormal gait with a higher adduction moment compared to age-matched controls in a gait analysis study presented at the British Orthopaedic Association Congress, here.
Total knee replacement surgery, however, did not improve overall gait and lower extremity joint loading in patients with osteoarthritis (OA), according to investigators.
“Final gait resulted in elevated moments and elevated co-contractions bilaterally, and this analysis persists despite the index joint having been replaced,” Andrew J. Metcalfe, MRCS, said. “We feel these joints are at risk for abnormal loading.”
Osteoarthritis effects
Metcalfe and colleagues at the Robert Jones and Agnes Hunt Orthopaedic Hospital, Oswestry, United Kingdom, the Betsi Cadwaladr University Health Board, North Wales and Cardiff University, Wales, conducted the gait analysis study to confirm if patients with knee osteoarthritis loaded joints in their lower limbs not affected by OA any differently, and if knee arthroplasty can adequately treat the problem.
“This is an important question. In previous work, we found 80% of patients with single joint knee [osteoarthritis] OA will develop bilateral disease over a longer period,” Metcalfe said.
Andrew J. Metcalfe
Metcalfe and colleagues studied the gait and took electromyography measurements in 20 patients with a mean age of 69 years with unilateral knee OA and performed the same studies in 20 patients aged 68 years mean, who served as controls. They used a 12-camera Vicon motion analysis system (Oxford, United Kingdom) equipped with three force plates and recorded muscle activity with electrodes that were attached to the medial and lateral hamstrings and quadriceps, bilaterally.
Investigators had 12-month follow-up data for 15 patients in the active group at the time the results were presented.
In the study group, the investigators saw “a significant increase in co-contraction bilaterally, resulting from the combined contraction of quadriceps and hamstrings, and that increases joint reaction forces beyond what is measured by gait analysis alone,” Metcalfe said.
Resolving this problem may involve providing patients with gait training, “although that’s a subject for future study,” he said.
Metcalfe noted that despite the few patients in the study, both the gait and the co-contraction results were statistically significant.
Take-home message
“We believe that our results demonstrate a learned ‘osteoarthritis’ gait pattern characterized by high impulses and co-contraction bilaterally, which persists when the index joint is treated. We have suggested that this might be described as a ‘walking on ice’ gait pattern as it is very similar to the pattern that people adopt when they walk on slippery surfaces, and may represent a desire for patients to prevent falls, slips or stumbles,” he said.
“The message to surgeons is that they cannot tell patients that loading of the other joints will return to normal following knee replacement, and ‘protecting the other joints’ should not be a reason to perform knee replacement, although we believe that with additional training and rehabilitation this may be possible to achieve in the future. We don’t yet have enough data to say whether early replacement is able to prevent this problem,” he said. – by Susan M. Rapp
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Disclosure: The study was funded by a research grant from Betsi Cadwaladr University Health Board, which also acted as sponsors for the study.