Knee buckling

Knee buckling often described as the knee “giving way” when one or both of your knees give out, is a symptom of knee instability that frequently affects older individuals, in particular those with knee pain and knee osteoarthritis (OA), and may be caused by muscle weakness and balance difficulties ¹. Knee buckling in older adults may increase the risk of falling, according to a study published online Feb. 8, 2016, by Arthritis Care & Research ¹. When your knee buckles, you can lose your balance and fall, which raises your risk of injury and even fractures. Repeated incidents also can limit your ability to climb stairs.

If it’s only happened once or twice, you may have just stumbled. However, if it keeps happening, it could be a sign of something else. Frequent knee buckling also raises your risk of falling and seriously injuring yourself, so it’s important to figure out the underlying cause.

Knee buckling and symptoms of impending falling may be treatable or at least prevented, but avoiding activities that precipitate buckling may limit function. Knee buckling may cause falls and fractures and may help to explain the increased risk for hip fracture in patients with osteoarthritis who have higher bone density than others their age and who, therefore, should be at diminished risk for fracture ².

Researchers studied 1,842 participants, 40% of whom were men, who were at high risk for knee osteoarthritis. At the end of 5 years, 16.8% reported regular knee buckling, and at the end of 7 years, those people were 1.6 to 2.5 times more likely to experience recurring falls, fear of falling, and poor confidence in their ability to balance. Bucklers at year 5 had a 1.6- to 2.5-times higher likelihood of recurrent falls, fear of falling, and poor balance confidence at year 7. Those who fell when a knee buckled at the start of the study had a 4.5-times, 2-times, and 3-times higher likelihood 2 years later of recurrent falls, significant fall injuries, and fall injuries that limited activity, respectively, and they were 4-times more likely to have poor balance.

If knee instability leads to frequent falls and fall-related injuries, exercises and other interventions that stabilize the knee may help maintain older individuals’ health and quality of life.

Strengthening the quadriceps muscles (front of the thighs) can help improve knee stability and reduce buckling, according to lead researcher Dr. Michael Nevitt, a professor of epidemiology and biostatistics at the University of California, San Francisco ¹. Balance exercises also might help, but the direct benefits have not yet been studied, he says.

Knee osteoarthritis (OA), also known as degenerative joint disease, is typically the result of wear and tear and progressive loss of articular cartilage ³. Osteoarthritis (OA) is a leading cause of musculoskeletal pain and disability where the knee is commonly affected ⁴. It is most common in elderly women and men. Knee osteoarthritis can be divided into two types, primary and secondary. Primary osteoarthritis is articular degeneration without any apparent underlying reason. Secondary osteoarthritis is the consequence of either an abnormal concentration of force across the joint as with post-traumatic causes or abnormal articular cartilage, such as rheumatoid arthritis (RA).

Osteoarthritis is typically a progressive disease that may eventually lead to disability. The intensity of the clinical symptoms may vary from each individual. However, they typically become more severe, more frequent, and more debilitating over time. The rate of progression also varies for each individual. Common clinical symptoms include knee pain that is gradual in onset and worse with activity, knee stiffness and swelling, pain after prolonged sitting or resting, and pain that worsens over time. Pain is dominant, becoming persistent and more limiting with disease progression, leading to disability, reduced quality of life, and often joint replacement ⁵. Pain results from a complex interaction between structural joint changes ⁶, physical impairments ⁷, and psychosocial factors ⁷. Evidence has shown that patients with symptomatic osteoarthritis experience fluctuations of relatively short durations in pain severity ⁸. These intense and intermittent pain fluctuations are called pain exacerbations or pain flares ⁹. Pain flares are often exacerbated during activities and are relieved with rest, although later in the disease course, pain can also occur at night and during rest ⁹.

A cross-sectional study suggested that almost 12% of participants with knee osteoarthritis had at least one event of knee buckling during the last 3 months and that buckling was associated with functional loss and limitation of daily activities ¹⁰. The study of Nguyen et al ¹¹ reported that within 3 months study period among those who suffered knee buckling, the overwhelming majority had two or more episodes of knee buckling during that time. For these participants, 74% reported 2-5 buckling episodes, 17% reported 6-10 episodes, and 9% reported 11 or more episodes ¹¹. Knee buckling and especially sensations of knee instability without buckling were found to be associated with fear of falling, poor balance confidence, activity limitations, and poor physical function ¹¹.

Treatment for knee osteoarthritis begins with conservative methods and progresses to surgical treatment options when conservative treatment fails. While medications can help slow the progression of rheumatoid arthritis (RA) and other inflammatory conditions, no proven disease-modifying agents for the treatment of knee osteoarthritis currently exist ¹².

Knee buckling causes

Knee buckling occurs mostly in persons with knee pain and frequent knee pain affects about 25% of adults ¹³. Many of these persons have osteoarthritis of the knee ¹⁴.

When knee buckling is discussed, it is identified as evidence of an internal derangement, such as an anterior cruciate ligament (ACL) tear ¹⁵. A search of MEDLINE for articles on knee instability (subject), buckling, or giving way revealed that articles on knee buckling or instability were found almost exclusively in the orthopedic literature, where it was noted as a complication of surgery ¹⁶; a hallmark symptom of ACL (anterior cruciate ligament) tear ¹⁷; or a consequence of specific, uncommon conditions, such as patellar dislocation ¹⁸. Thus, knee buckling is not generally described in native, uninjured knees.

When Felson and colleagues ¹⁹ examined the demographic and disease related attributes of persons who experienced knee buckling, they found that buckling was equally common in both sexes and did not increase in prevalence with age. However, knee buckling increased in prevalence with greater BMI (body mass index), occurring in only 7.7% of persons in the lowest quartile of BMI but in 17.6% of those in the highest quartile ¹⁹. The prevalence of knee pain and knee buckling was similar in the community cohort and in the Framingham Offspring Study cohort.

Knee buckling was far more common in knees with pain at any time in the past 30 days (14.1% of knees with pain experienced buckling) than in knees with no pain at all (2.1%) ¹⁹. The prevalence of buckling was 26.7% among knees with pain rated as severe compared with 9.9% among knees with pain rated as mild.

Knee buckling was more common in knees with radiographic osteoarthritis in the tibiofemoral joint than in those without this condition (11.0% vs. 4.7%). Among knees with radiographic osteoarthritis, buckling occurred most often in knees with both tibiofemoral and patellofemoral disease ¹⁹. Even so, most persons with knee buckling had pain in the affected knee but did not have osteoarthritis in that knee on radiography.

Knee osteoarthritis is classified as either primary or secondary, depending on its cause. Primary knee osteoarthritis is the result of articular cartilage degeneration without any known reason. This is typically thought of as degeneration due to age as well as wear and tear. Secondary knee osteoarthritis is the result of articular cartilage degeneration due to a known reason ²⁰.

Possible causes of secondary knee osteoarthritis

• Posttraumatic
• Postsurgical
• Congenital or malformation of the limb
• Malposition (Varus/Valgus)
• Scoliosis
• Rickets
• Hemochromatosis
• Chondrocalcinosis
• Ochronosis
• Wilson disease
• Gout
• Pseudogout
• Acromegaly
• Avascular necrosis
• Rheumatoid arthritis
• Infectious arthritis
• Psoriatic arthritis
• Hemophilia
• Paget disease
• Sickle cell disease

Risk factors for knee osteoarthritis

• Modifiable
  • Articular trauma
  • Occupation – prolonged standing and repetitive knee bending
  • Muscle weakness or imbalance
  • Weight
  • Health – metabolic syndrome
• Non-modifiable
  • Gender – females more common than males
  • Age
  • Genetics
  • Race

The prevalence of knee buckling increased with the number of nonknee joints in either leg that were painful. For example, participants who reported hip pain in addition to knee pain also reported buckling more often than those who reported only knee pain. Finally, quadriceps strength was related to buckling, which occurred in 8.7% of knees in the lowest quartile of quadriceps strength compared with 3.0% of those in the highest quartile ¹⁹. Among right-knee MRIs that were read, 101 knees had buckling; of these, only 12 (11.9%) had ACL tears. Of MRIs of knees without buckling, 42 of 1159 (3.6%) had ACL tears (3.6%).

When Felson and colleagues ¹⁹ examined risk factors associated with knee buckling, they found that buckling was inversely related to quadriceps strength and that quadriceps strength was associated with knee buckling risk independent of age, sex, and BMI ¹⁹.

Knee buckling was also associated with the overall level of physical function. Fifty percent of participants reporting any episodes of buckling and more than half of participants who had more than 1 episode were either limited a little or limited a lot in their overall activities ¹⁹. Participants with buckling had a significantly increased risk for being limited a little or limited a lot (odds ratio for “limited a lot,” 1.9) ¹⁹. Even after adjustment for the degree of pain in the knee and for age, sex, and BMI, knee buckling remained independently associated with physical limitation.

Of participants with knee buckling, roughly two thirds noted a little or a lot of limitation on climbing stairs, and even after adjustment for pain, buckling was associated with limitations in climbing stairs ¹⁹. Roughly half of participants with buckling accomplished less than they would like and were limited in the kind of work that they could do. The odds for work limitation among participants with buckling was increased more than 3-fold compared with those without buckling, an increased risk that persisted after adjustment.

Persons with knee buckling had higher mean Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) disability scores than did those without buckling. Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) questionnaire, a validated instrument for assessment of knee pain and disability ²¹. The higher score for disability among persons with knee buckling was independent of pain severity, weakness, age, and BMI.

Differential diagnosis

Any potential cause of local or diffuse knee pain should be considered in the differential diagnosis of knee osteoarthritis.

• Hip arthritis
• Low back pain
• Spinal stenosis
• Patellofemoral syndrome
• Meniscal tear
• Pes anserine bursitis
• Infections arthritis
• Gout
• Pseudogout
• Iliotibial band syndrome
• Collateral or cruciate ligament injury

Knee buckling symptoms

Patients typically present to their healthcare provider with the chief complaint of knee pain and knee buckling. It is essential to obtain a detailed history of their symptoms. Pay careful attention to the history as knee pain can be referred from the lumbar spine or the hip joint. It is equally important to obtain a detailed medical and surgical history to identify any risk factors associated with secondary knee osteoarthritis.

The history of the present illness should include the following:

• Onset of symptoms
• Specific location of pain
• Duration of pain and symptoms
• Characteristics of the pain
• Alleviating and aggravating factors
• Any radiation of pain
• Specific timing of symptoms
• Severity of symptoms
• The patient’s functional activity

Clinical symptoms of knee osteoarthritis

Knee pain

• Typically of gradual onset
• Worse with prolonged activity
• Worse with repetitive bending or stairs
• Worse with inactivity
• Worsening over time
• Better with rest
• Better with ice or anti-inflammatory medication
• Knee stiffness
• Knee swelling
• Decreased ambulatory capacity

Knee buckling diagnosis

Physical examination of the knee should begin with a visual inspection. With the patient standing, look for periarticular erythema and swelling, quadriceps muscle atrophy, and varus or valgus deformities. Observe gait for signs of pain or abnormal motion of the knee joint that can be indicative of ligamentous instability. Inspect the surrounding skin for the presence and location of any scars from previous surgical procedures, overlying evidence of trauma, or any soft tissue lesions.

Range of motion (ROM) testing is a very important aspect of the knee exam. Active and passive ROM with regard to flexion and extension should be assessed and documented.

Palpation along the bony and soft tissue structures is an essential part of any knee exam. The palpatory exam can be broken down into the medial, midline, and lateral structures of the knee.

Areas of focus for the medial aspect of the knee:

• Vastus medialis obliquus
• Superomedial pole patella
• Medial facet of the patella
• Origin of the medial collateral ligament (MCL)
• Midsubstance of the MCL
• Broad insertion of the MCL
• Medial joint line
• Medial meniscus
• Pes anserine tendons and bursa

Areas of focus for the midline of the knee:

• Quadricep tendon
• Suprapatellar pouch
• Superior pole patella
• Patellar mobility
• Prepatellar bursa
• Patellar tendon
• Tibial tubercle

Areas of focus for the lateral aspect of the knee:

• Iliotibial band
• Lateral facet patella
• Lateral collateral ligament (LCL)
• Lateral joint line
• Lateral meniscus
• Gerdy’s tubercle

A thorough neurovascular exam should be performed and documented. It is important to assess the strength of the quadriceps and hamstring muscles as these often times will become atrophied in the presence of knee pain. A sensory exam of the femoral, peroneal, and tibial nerve should be assessed as there may be concomitant neurogenic symptoms associated. Palpation of a popliteal, dorsalis pedis, and posterior tibial pulse is important as any abnormalities may raise the concern for vascular problems.

Other knee tests may be performed, depending on the clinical suspicion based on the history.

Special knee tests

• Patella apprehension – patellar instability
• J-sign – patellar maltracking
• Patella compression/grind – chondromalacia or patellofemoral arthritis
• Medial McMurray – a medial meniscus tear
• Lateral McMurray – lateral meniscus tear
• Thessaly test – a meniscus tear
• Lachman – anterior cruciate ligament (ACL) injury
• Anterior drawer – ACL injury
• Pivot shift – ACL injury
• Posterior drawer – posterior cruciate ligament (PCL) injury
• Posterior sag – PCL injury
• Quadriceps active test – PCL injury
• Valgus stress test – MCL injury
• Varus stress test – LCL injury

Imaging studies

In addition to a thorough history and physical, radiographic imaging is required. The recommend views include standing anteroposterior (AP), standing lateral in extension, and a skyline view of the patella. A standing 45-degree posteroanterior (PA) view of the knee may be obtained which gives a better assessment of the weight-bearing surface of the knee. Occasionally, long leg standing films will be obtained to view the degree of deformity and overall alignment of the lower extremity. It is important to understand that radiographs of the knee must be obtained with the patient standing. This gives an accurate representation of the joint space narrowing present. Often, films will be taken with the patient supine which gives a false sense of joint space and alignment and therefore should not be used is the evaluation of suspected knee osteoarthritis ²².

Radiographic findings of osteoarthritis

• Joint space narrowing
• Osteophyte formation
• Subchondral sclerosis
• Subchondral cysts

Knee giving out treatment

Treatment for knee osteoarthritis can be broken down into non-surgical and surgical management. Initial treatment begins with non-surgical modalities and moves to surgical treatment once the non-surgical methods are no longer effective. A wide range of non-surgical modalities is available for the treatment of knee osteoarthritis. These interventions do not alter the underlying disease process, but they may substantially diminish pain and disability ²³.

Non-surgical treatment

Non-Surgical Treatment Options ²²:

• Patient education
• Activity modification
• Physical therapy
• Weight loss
• Knee bracing
• Acetaminophen
• Nonsteroidal anti-inflammatory drugs (NSAIDs)
• COX-2 inhibitors
• Glucosamine and chondroitin sulfate
• Corticosteroid injections
• Hyaluronic acid (HA)

The first-line treatment for all patients with symptomatic knee osteoarthritis includes patient education and physical therapy. A combination of supervised exercises and a home exercise program have been shown to have the best results. These benefits are lost after 6 months if the exercises are stopped. The American Academy of Orthopedic Surgeons recommends this treatment.

A typical exercise program should include:

• Range-of-motion exercises to keep your joints and muscles flexible.
• Strengthening exercises, especially ones that target your quadriceps, such as walking up hills or stairs.
• Balance and agility exercises such as yoga or tai chi.
• Aerobic exercise that’s easy on the joints, such as swimming, walking, or bicycling, to keep your heart and lungs healthy and control your weight.

Weight loss is valuable in all stages of knee osteoarthritis. It is indicated in patients with symptomatic arthritis with a body mass index greater than 25. The best recommendation to achieve weight loss is with diet control and low-impact aerobic exercise. There is moderate evidence for weight loss based on the American Academy of Orthopedic Surgeons guidelines.

Knee bracing in the setting of osteoarthritis includes unloader-type braces which shift the load away from the involved knee compartment. This may be useful in the setting where either the lateral or medial compartment of the knee is involved such as in a valgus or varus deformity.

Drug therapy is also the first-line treatment for patients with symptomatic osteoarthritis. There are a wide variety of NSAIDs available, and the choice should be based on physician preference, patient acceptability, and cost. The duration of treatment with NSAIDs should be based on effectiveness, adverse effects, and past medical history. There is strong evidence for NSAID use based on the American Academy of Orthopedic Surgeons guidelines.

Glucosamine and chondroitin sulfate are available as dietary supplements. They are structural components of articular cartilage, and the thought is that a supplement will aid in the health of articular cartilage. No strong evidence exists that these supplements are beneficial in knee osteoarthritis; in fact, there is strong evidence against the use according to the American Academy of Orthopedic Surgeons guidelines. There are no major downsides to taking the supplement. If the patient understands the evidence behind these supplements and is willing to try the supplement, it is a relatively safe option. Any benefit gained from supplementation is likely due to a placebo effect.

Intra-articular corticosteroid injections may be useful for symptomatic knee osteoarthritis, especially where there is a considerable inflammatory component. The delivery of the corticosteroid directly into the knee may reduce local inflammation associated with osteoarthritis and minimize the systemic effects of the steroid.

Intra-articular hyaluronic acid (HA) injections are another injectable option for knee osteoarthritis. hyaluronic acid is a glycosaminoglycan that is found throughout the human body and is an important component of synovial fluid and articular cartilage. hyaluronic acid breaks down during the process of osteoarthritis and contributes to the loss of articular cartilage as well as stiffness and pain. Local delivery of hyaluronic acid into the joint acts as a lubricant and may help increase the natural production of hyaluronic acid in the joint. Depending on the brand of hyaluronic acid, it can either be produced from avian cells or bacterial cells in the laboratory and therefore must be used with caution in those with avian allergies. While this is a prevalent treatment option, it is not highly supported in the literature, and there is strong evidence against its use based on the American Academy of Orthopedic Surgeons guidelines.

Surgical treatment

Surgical Treatment Options ²⁴:

• Osteotomy
• Unicompartmental knee arthroplasty
• Total knee arthroplasty (total knee replacement)

A high tibial osteotomy may be indicated for unicompartmental knee osteoarthritis associated with malalignment. Typically an high tibial osteotomy is done for varus deformities where the medial compartment of the knee is worn and arthritic. The ideal patient for an high tibial osteotomy would be a young, active patient in whom arthroplasty would fail due to excessive component wear. An high tibial osteotomy preserves the actual knee joint, including the cruciate ligaments, and allows the patient to return to high-impact activities once healed. It does require additional healing time compared to an arthroplasty, is more prone to complications, depends on bone and fracture healing, is less reliable for pain relief, and ultimately does not replace cartilage that is already lost or repair any remaining cartilage. An osteotomy will delay the need for an arthroplasty for up to 10 years.

Indications for high tibial osteotomy:

• Young (less than 50 years old), active patient
• Healthy patient with good vascular status
• Non-obese patients
• Pain and disability interfering with daily life
• Only one knee compartment is affected
• Compliant patient who will be able to follow postoperative protocol

Contraindications for high tibial osteotomy:

• Inflammatory arthritis
• Obese patients
• Knee flexion contracture greater than 15 degrees
• Knee flexion less than 90 degrees
• If the procedure will need greater than 20 degrees of deformity correction
• Patellofemoral arthritis
• Ligamentous instability

A unicompartmental knee arthroplasty also is indicated in unicompartmental knee osteoarthritis. It is an alternative to an high tibial osteotomy and a total knee replacement. It is indicated for older patients, typically 60 years or older, and relatively thin patients; although, with newer surgical techniques the indications are being pushed.

Indications for unicompartmental knee arthroplasty:

• Older (60 years or older), lower demand patients
• Relatively thin patients

Contraindications for unicompartmental knee arthroplasty:

• Inflammatory arthritis
• ACL deficiency
• Fixed varus deformity greater than 10 degrees
• Fixed valgus deformity greater than 5 degrees
• Arc of motion less than 90 degrees
• Flexion contracture greater than 10 degrees
• Arthritis in more than one compartment
• Younger, higher activity patients or heavy laborers
• Patellofemoral arthritis

A total knee replacement is the surgical treatment option for patients failing conservative management and those with osteoarthritis in more than one compartment. It is regarded as a valuable intervention for patients who have severe daily pain along with radiographic evidence of knee osteoarthritis.

Indications for total knee replacement:

• Symptomatic knee osteoarthritis in more than one compartment
• Failed non-surgical treatment options

Contraindications for total knee replacement:

• Absolute contraindications
  
  • Active or latent knee infection
  • Presence of active infection elsewhere in the body
  • Incompetent quadriceps muscle or extensor mechanism
• Relative contraindications
  • Neuropathic arthropathy
  • Poor soft tissue coverage
  • Morbid obesity
  • Noncompliance due to major psychiatric disorder or alcohol or drug abuse
  • Insufficient bone stock for reconstruction
  • Poor health or presence of comorbidities that make the patient an unsuitable candidate for major surgery and anesthesia
  • Patient’s poor motivation or unrealistic expectations
  • Severe peripheral vascular disease

Advantages of unicompartmental knee arthroplasty versus total knee replacement

• Faster rehabilitation and quicker recovery
• Less blood loss
• Less morbidity
• Less expensive
• Preservation of normal kinematics
• Smaller incision
• Less postsurgical pain and shorter hospital stay

Advantages of unicompartmental knee arthroplasty versus high tibial osteotomy

• Faster rehabilitation and quicker recovery
• Improved cosmesis
• Higher initial success rate
• Fewer short-term complications
• Lasts longer
• Easier to convert to total knee replacement

Complications

Complications associated with non-surgical treatment are largely associated with NSAID use.

Common adverse effects of NSAID use:

• Stomach pain and heartburn
• Stomach ulcers
• A tendency to bleed, especially while taking aspirin
• Kidney problems

Common adverse effects of intra-articular corticosteroid injection:

• Pain and swelling (cortisone flare)
• Skin discoloration at the site of injection
• Elevated blood sugar
• Infection
• Allergic reaction

Common adverse effects of intra-articular hyaluronic acid (HA) injection:

• Injection site pain
• Muscle pain
• Trouble walking
• Fever
• Chills
• Headache

Complications Associated with high tibial osteotomy:

• Recurrence of deformity
• Loss of posterior tibial slope
• Patella baja
• Compartment syndrome
• Peroneal nerve palsy
• Malunion or nonunion
• Infection
• Persistent pain
• Blood clot

Complications Associated with unicompartmental knee arthroplasty:

• Stress fracture of the tibia
• Tibial component collapse
• Infection
• Osteolysis
• Persistent pain
• Neurovascular injury
• Blood clot

Complications Associated with total knee replacement:

• Infection
• Instability
• Osteolysis
• Neurovascular injury
• Fracture
• Extensor mechanism rupture
• Patellar maltracking
• Patellar clunk syndrome
• Stiffness
• Peroneal nerve palsy
• Wound complications
• Heterotopic ossification
• Blood clot.

References

1. Michael C. Nevitt, Irina Tolstykh, Najia Shakoor, Uyen S. Nguyen, Neil A. Segal, Cora Lewis, David T. Felson. Symptoms of Knee Instability are Risk Factors for Recurrent Falls. Arthritis Care & Research, 2015; DOI: 10.1002/acr.22811 http://doi.wiley.com/10.1002/acr.22811
2. Arden NK, Crozier S, Smith H, Anderson F, Edwards C, Raphael H, et al. Knee pain, knee osteoarthritis, and the risk of fracture. Arthritis Rheum. 2006; 55:610-5.
3. Hsu H, Siwiec RM. Knee Osteoarthritis. [Updated 2019 Jun 17]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK507884
4. Hunter D, Schofield D, Callander Emily. The individual and socioeconomic impact of osteoarthritis. Nat Rev Rheumatol. 2014 Jul;10(7):437–41. doi: 10.1038/nrrheum.2014.44
5. Neogi T. The epidemiology and impact of pain in osteoarthritis. Osteoarthritis Cartilage. 2013 Sep;21(9):1145–53. doi: 10.1016/j.joca.2013.03.018. http://linkinghub.elsevier.com/retrieve/pii/S1063-4584(13)00760-7
6. Hunter D, Guermazi A, Roemer F, Zhang Y, Neogi T. Structural correlates of pain in joints with osteoarthritis. Osteoarthritis Cartilage. 2013 Sep;21(9):1170–8. doi: 10.1016/j.joca.2013.05.017
7. Busija L, Osborne R, Roberts C, Buchbinder Rachelle. Systematic review showed measures of individual burden of osteoarthritis poorly capture the patient experience. J Clin Epidemiol. 2013 Aug;66(8):826–37. doi: 10.1016/j.jclinepi.2013.03.011
8. Neogi T. The epidemiology and impact of pain in osteoarthritis. Osteoarthritis Cartilage. 2013 Sep;21(9):1145–53. doi: 10.1016/j.joca.2013.03.018
9. Hunter D, McDougall J, Keefe Francis J. The symptoms of osteoarthritis and the genesis of pain. Rheum Dis Clin North Am. 2008 Aug;34(3):623–43. doi: 10.1016/j.rdc.2008.05.004
10. Felson D, Niu J, McClennan C, Sack B, Aliabadi P, Hunter D, Guermazi Ali, Englund Martin. Knee buckling: prevalence, risk factors, and associated limitations in function. Ann Intern Med. 2007 Oct 16;147(8):534–40.
11. Nguyen U-S D T. Felson DT, Niu J, White DK, Segal NA, Lewis CE, Rasmussen M, Nevitt M C. The impact of knee instability with and without buckling on balance confidence, fear of falling and physical function: the Multicenter Osteoarthritis Study. Osteoarthritis Cartilage. 2014 Apr;22(4):527–34. doi: 10.1016/j.joca.2014.01.008
12. Springer BD. Management of the Bariatric Patient. What Are the Implications of Obesity and Total Joint Arthroplasty: The Orthopedic Surgeon’s Perspective? J Arthroplasty. 2019 Jul;34(7S):S30-S32.
13. Peat G, McCarney R, Croft P. Knee pain and osteoarthritis in older adults: a review of community burden and current use of primary health care. Ann Rheum Dis. 2001;60:91-7.
14. Hannan MT, Felson DT, Pincus T. Analysis of the discordance between radiographic changes and knee pain in osteoarthritis of the knee. J Rheumatol. 2000;27:1513-7.
15. Kalunian KC, Brion PH, Wollaston SJ. Clinical manifestations of osteoarthritis. In: Rose BD, ed. UpToDate Online, version 15.1. Waltham, MA: Up-ToDate; 2007.
16. Yercan HS, Ait Si Selmi T, Sugun TS, Neyret P. Tibiofemoral instability in primary total knee replacement: A review Part 2: diagnosis, patient evaluation, and treatment. Knee. 2005;12:336-40.
17. 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; discussion 283-6.
18. Neyret P, Robinson AH, Le Coultre B, Lapra C, Chambat P. Patellar tendon length—the factor in patellar instability? Knee. 2002;9:3-6.
19. Knee Buckling: Prevalence, Risk Factors, and Associated Limitations in Function. Ann Intern Med. 2007;147:534-540. DOI: 10.7326/0003-4819-147-8-200710160-00005
20. Manlapaz DG, Sole G, Jayakaran P, Chapple CM. Risk Factors for Falls in Adults with Knee Osteoarthritis: A Systematic Review. PM R. 2019 Jul;11(7):745-757.
21. Bellamy N, Buchanan WW, Goldsmith CH, Campbell J, Stitt LW. Validation study of WOMAC: a health status instrument for measuring clinically important patient relevant outcomes to antirheumatic drug therapy in patients with osteoarthritis of the hip or knee. J Rheumatol. 1988;15:1833-40.
22. Afzali T, Fangel MV, Vestergaard AS, Rathleff MS, Ehlers LH, Jensen MB. Cost-effectiveness of treatments for non-osteoarthritic knee pain conditions: A systematic review. PLoS ONE. 2018;13(12):e0209240
23. Collins NJ, Hart HF, Mills KAG. Osteoarthritis year in review 2018: rehabilitation and outcomes. Osteoarthr. Cartil. 2019 Mar;27(3):378-391.
24. Aweid O, Haider Z, Saed A, Kalairajah Y. Treatment modalities for hip and knee osteoarthritis: A systematic review of safety. J Orthop Surg (Hong Kong). 2018 May-Aug;26(3):2309499018808669