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Knee Buckling: Prevalence, Risk Factors, and Associated Limitations in Function

David T. Felson, MD, MPH; Jingbo Niu, DS; Christine McClennan, MPH; Burton Sack, MD; Piran Aliabadi, MD; David J. Hunter, MD, PhD; Ali Guermazi, MD; and Martin Englund, MD, PhD
[+] Article, Author, and Disclosure Information

From Boston University School of Medicine, Hebrew SeniorLife, Brigham and Women's Hospital, and Boston Medical Center, Boston, Massachusetts.

Acknowledgments: The authors thank the participants of the Framingham Osteoarthritis Study for helping them perform this study.

Grant Support: By grants AR47785 and AG18393 from the National Institutes of Health and contract N01-HC-25195 for the National Heart, Lung, and Blood Institute's Framingham Heart Study.

Potential Financial Conflicts of Interest: None disclosed.

Requests for Single Reprints: David T. Felson, MD, MPH, Clinical Epidemiology Unit, Suite 200, Boston University School of Medicine, 650 Albany Street, Boston, MA 02118; e-mail, jendez@bu.edu.

Current Author Addresses: Drs. Felson, Niu, Sack, Hunter, and Englund: Clinical Epidemiology Unit, Suite 200, Boston University School of Medicine, 650 Albany Street, Boston, MA 02118.

Ms. McClennan: Institute for Aging Research, Hebrew SeniorLife, 1200 Centre Street, Boston, MA 02131.

Dr. Aliabadi: Department of Radiology, Brigham and Women's Hospital, 75 Francis Street, Boston, MA 02115.

Dr. Guermazi: Department of Radiology, 818 Harrison Avenue, Boston Medical Center, Boston, MA 02118.

Author Contributions: Conception and design: D.T. Felson, M. Englund.

Analysis and interpretation of the data: D.T. Felson, J. Niu, A. Guermazi, D.J. Hunter, M. Englund.

Drafting of the article: D.T. Felson.

Critical revision of the article for important intellectual content: J. Niu, C. McClennan, B. Sack, P. Aliabadi, A. Guermazi, D.J. Hunter, M. Englund.

Final approval of the article: C. McClennan, A. Guermazi.

Provision of study materials or patients: D.T. Felson, B. Sack.

Statistical expertise: J. Niu.

Obtaining of funding: D.T. Felson.

Administrative, technical, or logistic support: D.T. Felson, J. Niu, C. McClennan.

Collection and assembly of data: D.T. Felson, J. Niu, C. McClennan, B. Sack, P. Aliabadi.

Ann Intern Med. 2007;147(8):534-540. doi:10.7326/0003-4819-147-8-200710160-00005
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The 2351 participants ranged in age from 36 to 94 years (median, 63.5 years). Two hundred seventy-eight participants (11.8%) experienced at least 1 episode of buckling of either knee in the past 3 months; of these participants, 217 (78.1%) had more than 1 episode of knee buckling and 35 (12.6%) fell during an episode. Of persons with knee buckling, 136 reported walking, 97 reported stair climbing, and 71 reported twisting or turning at the time of buckling; some reported more than 1 such activity. No specific other activity was common during buckling.

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Grahic Jump Location
Appendix Figure 1.
Study flow diagram: the Framingham Offspring Study cohort.

ACL = anterior cruciate ligament; MRI = magnetic resonance imaging.

Grahic Jump Location
Grahic Jump Location
Appendix Figure 2.
Study flow diagram: the Framingham Osteoarthritis Study community cohort.

ACL = anterior cruciate ligament. *Members of Framingham Offspring Study, positive screening for rheumatoid arthritis, magnetic resonance imaging (MRI) contraindicated, bilateral knee replacement, dementia or terminal cancer, or planned to move from area. †Declined to participate because of cancer, chronic illness, no interest when received full details of the study, no reason given, no time, declined MRI or radiography, or other reasons. ‡Not done because of claustrophobia, medical contraindications, or problems with scheduling.

Grahic Jump Location




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Submit a Comment/Letter
Knee instability or pain-related reflexes in buckling, giving way, or giving out?
Posted on November 16, 2007
Samuel Betts, PT, DPT, MOMT, FAAOMPT
No Affiliation
Conflict of Interest: None Declared

Knee instability may present symptomatically as buckling, giving way, or giving out, and is often associated with rupture of the anterior cruciate ligament. Collateral ligament sprains may cause medial or lateral knee instability and buckling (1). Proposed mechanisms include ligamentous defects (1), thigh muscle atrophy or fatigue (1, 2), stretch reflex alterations (3), and knee joint changes, e.g., osteoarthritis (OA) (4). Few studies were performed of knee instability symptoms in the general population, and the report of Felson et al (4) is welcomed.

In that community study (4), knee buckling or having given way in a 3 month interval was more frequent in subjects having particular characteristics. Knee instability was more frequent in those having had pain, aching, or stiffness in either knee, over a 30 day interval (14.1 %) vs those responding negatively (2.1 %). Persons having highest body mass index (31.3 + kg/m2 ) had comparably high prevalence of knee symptoms (17.6 %), as did those with a history of knee injury (15.7 %), and greater radiographic evidence of OA (17.7 %). Quadriceps strength was inversely and independently related to the knee symptoms (Table 2, 4). They were also independently associated with worse physical functioning in personal activities and work abilities (4).

The recent report (4) is helpful for the physical therapist, internist, and rheumatologist, but a few points deserve clarification for patient management and for future research. Causal inferences or mechanisms cannot be interpreted from a historical or cross-sectional study design (4). However, greater specification of the instability event could help direct management. Giving way with vs without pain may infer mainly pain-related alterations of thigh muscle reflex activation vs biomechanical instability. As indicated (4), muscle strengthening and balance training are advisable to treat biomechanical instability. Pain- related instability may also benefit from such more directed therapy.

The terms buckling, giving way, or giving out have not been well defined in medical dictionaries or texts. One orthopedic text (1) described giving way as, "a sudden weakness in the leg that causes the leg to go into mild hyperextension or flexion" (presumably from neutral stance). Symptoms of giving way have also been associated with knee instability and displacements (2, 3, 5). Giving way was attributed to altered stretch reflex excitability, rather than to instability, in one study, without indication of pain symptoms (3). Future standardization of terminology and specification of event circumstances may likely improve data accuracy in future research.


1. D'Amato M, Bach BR, Jr. Knee injuries. In: Brotzman SB and Wilk KE (eds), clinical orthopedic rehabilitation, 2nd ed, Mosby, Inc. Philadelphia, 2003; Ch 4, 251-370.

2. Melnyk M, Gollhofer A. Submaximal fatigue of the hamstrings impairs specific reflex components and knee stability. Knee Surg Sports Traumatol Arthrosc. 2007; 15: 525-32.

3. Melnyk M, Faist M, Gothner M, Claes L, Friemert B. Changes in stretch reflex excitability are related to "giving way" symptoms in patients with anterior cruciate ligament rupture. J Neurophysiol. 2007; 97: 474-80.

4. Felson DT, Niu J, McClennan C, Sack B, Aliabadi P, Hunter DJ, et al. Knee buckling: prevalence, risk factors, and associated limitations in function. Ann Intern Med. 2007; 147: 534-40.

5. Houck J, Lerner A, Gushue D, Yack HJ. Self-reported giving way episode during a stepping-down task: case report of a subject with an ACL- deficient knee. J Orthop Sports Phys Ther. 2003; 33: 273-82.

Samuel J Betts, PT, DPT, MOMT, FAAOMPT Director of Rehabilitation Services Midwest Orthopaedic Center Peoria, IL 61614

Alfonse T Masi, MD, DR.P.H. Professor of Medicine University of Illinois College of Medicine at Peoria Peoria, IL 61656

Conflict of Interest:

None declared

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Summary for Patients

Knee Buckling in Older Adults

The summary below is from the full report titled “Knee Buckling: Prevalence, Risk Factors, and Associated Limitations in Function.” It is in the 16 October 2007 issue of Annals of Internal Medicine (volume 147, pages 534-540). The authors are D.T. Felson, J. Niu, C. McClennan, B. Sack, P. Aliabadi, D.J. Hunter, A. Guermazi, and M. Englund.


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