May also bring loss of confidence in balance and increased fear of falling.
Older individuals with knee osteoarthritis (OA) who reported falling when a knee buckled had a significantly increased likelihood of additional falls and of developing adverse consequences of falling, a large prospective study found.
A fall related to knee buckling was associated with a 4.5-fold increase in recurrent falls (OR 4.5, 95% CI 2.34-8.71) during the subsequent 2 years, as well as a two-fold increase in risk of experiencing a significant injury from a fall (OR 2.23, 95% CI 1.07-4.67) and a three-fold increase in having an injury that resulted in activity limitations (OR 2.95, 95% CI 1.41-6.17), according to Michael C. Nevitt, PhD, of the University of California San Francisco, and colleagues.
Patients who fell with knee buckling also were more likely to have poor confidence in their balance 2 years later (OR 4.17, 95% CI 1.80-9.68) and to report a fear of falling (OR 2.10, 95% CI 1.02-4.33), the researchers reported in Arthritis Care & Research.
“Knee buckling, the sudden loss of postural support across the knee during weight bearing, often described as a knee ‘giving way,’ is a symptom of knee instability that frequently affects older individuals, especially those with knee pain,” Nevitt and colleagues wrote.?
In an earlier study of patients enrolled in the Multicenter Osteoarthritis Study (MOST), 18% reported having an episode of knee buckling in the previous 3 months and one in eight of those patients had a fall associated with the knee giving way. Moreover, almost 20% had other, less severe symptoms of knee instability such as feelings of the joint shifting or slipping.
To more extensively quantify the risks associated with knee buckling, the researchers conducted longitudinal and cross-sectional analyses of participants in MOST, who were community-dwelling adults ages 50 to 79 enrolled in 2003 to 2005.
Baseline for the current analysis was the 60-month clinic visit.
Of 1,842 eligible participants at that visit, 310 (16.8%) reported at least one episode of knee buckling in the past 3 months. Almost 30% reported the lesser symptoms of knee shifting or slipping, and 8.8% had both. Of those experiencing knee buckling at baseline, 92% had either radiographic knee OA or knee pain on most of the past 30 days.
The knee bucklers had a mean BMI of 31.6 kg/m2 compared with 30.1 kg/m 2 for the 1,532 nonbucklers, and they were more likely to have comorbidities, depression, and chronic hip pain, as well as higher foot pain scores. They were also more likely to have taken prescription narcotic analgesics in the past 30 days. Only about 2% of the sample had probable cognitive impairment.
Two years later, 14.1% of patients who had reported knee buckling at 60 months had at least two recurrent falls in the preceding 12 months. That translated to a 1.6 to 2.5-fold greater odds of multiple falls, fear of falling, and poor balance confidence at 84-month follow-up.
In addition, 60-month bucklers were more likely to have had significant and activity-limiting fall-related injuries in the 12 months preceding baseline, with adjusted odds ratios of 2.38 (95% CI 1.60-3.54) and 1.96 (95% CI 1.29-3.00), respectively. At 84 months, although bucklers had no increased risk of fall-related injuries, they were at greater risk for poor balance confidence (OR 2.47, 95% CI 1.58-3.85) and fear of falling (OR 1.62, 95% CI 1.16-2.26).
“The results of this study should make all of us who treat people with knee osteoarthritis or chronic knee pain take the patient’s complaint of knee instability more seriously,” commented G. Kelley Fitzgerald, PT, PhD, of the Physical Therapy Clinical and Translational Research Center, University of Pittsburgh, who was not involved in the study.
“Up until now, I think there may have been mixed opinions whether the complaint of knee instability in patients with knee osteoarthritis was more of an annoyance,” Fitzgerald said.
He cautioned, however, that knee instability may be multifactorial, and although beneficial, leg-strengthening exercises may be insufficient for all patients. Some with knee OA could have permanent sensory deficits that will require new or modified strategies for moving and dealing with instability. “These patients might benefit from balance and agility training and other treatment techniques that may improve neuromuscular control,” Fitzgerald said.
He pointed to a need for more research to understand the factors that drive the different sensations of knee buckling, shifting, and slipping and to match effective treatments accordingly.
“Studies should examine the effects of strengthening, balance, agility, and other neuromuscular control training activities, and bracing or combinations of these approaches on complaints of knee instability, falls, fear of falling, and balance confidence,” he added.
“Finding effective treatments for knee instability should be a priority and may help prevent knee buckling and falls and their adverse consequences in older persons with knee pain,” the study authors wrote.
Limitations of the study included the exclusion of knee replacement recipients and the lack of distinction between indoor and outdoor falls. “If buckling is preferentially associated with either indoor or outdoor falls, combining them may cause us to underestimate the association of knee instability with falls,” they wrote.
In addition, the method of assessing falls was by 12-month recall rather than weekly or monthly, and without memory aids such as diaries or calendars.