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Flare-ups in Osteoarthritis

Flare ups in oa

Osteoarthritis is a chronic condition that affects many people worldwide. One of the most common symptoms is an acute pain flare-up. Flare-ups in osteoarthritis can lead to nocturnal awakening, knee effusion, morning stiffness, and limping. This blog explores the concept of acute flares in osteoarthritis. It also explores the fear of having an acute flare-up and the possible triggers for it.

Flare-ups in Osteoarthritis: What are they?

Parry et al. (2018) investigated what definitions of acute flares existed in the literature. However, there isn’t currently a single, accepted definition of an OA flare, their analysis of 69 published papers points to several key characteristics.

They found that the onset or worsening of symptoms and signs beyond normal day-to-day variability was largely used to define acute flare-ups in osteoarthritis. This includes an increased pain sensitivity or worsening of symptoms related to swelling, inflammation, erythema, warmth, limping, morning stiffness, nocturnal awakening, and nocturnal pain. 

There is no defined time frame for the flare-up to last. In many studies, a minimal pain intensity threshold is required to consider someone having pain flare-ups. Many studies required a minimal pain intensity of 4 out of 10 on the VAS. When the WOMAC was used, the studies mostly focused on the question of reported pain during walking on a flat surface. The fact that there is no minimum duration of the flare-up defined, makes it difficult to distinguish acute flares from day-to-day variability. In that case, a patient-diary might help.

flare-oa questionnaire
From: Parry et al., Osteoarthritis Cartilage. (2019)

Triggers – is the weather to blame?

You might have heard from many people affected by osteoarthritis that the weather influences their symptoms. But is the weather to blame? 

Changes in local joint stress could be one of the triggers for acute pain flare-ups in osteoarthritis. It is believed that a key factor in the etiopathogenesis of OA is cumulative low-level microtrauma caused by abnormal or recurring mechanical stress. (Brandt et al. 2008)

However, triggers do not only exist in the biomechanical aspect. Thomas et al. (2021) found that multiple activity-related, psychosocial, and environmental exposures are implicated in triggering flares. 

“The strongest positive association was with the knee giving way (OR 9.06: 95%CI 5.86, 13.99). The strongest positive physical activity association was with squatting or kneeling (OR [‘a lot’ vs ‘not at all’], 3.30: 95%CI 1.95, 5.59). Three exposures were inversely associated with flares: sitting for long periods without a break (OR 0.67: 95%CI 0.46, 0.98), reducing or missing planned medication (OR 0.34: 95%CI 0.18, 0.63), and cough, cold or minor infection (OR 0.72: 95%CI 0.52, 0.99). The frequency of most physical activity exposures suggested a graded relationship with the risk of flare (a lot > a little > not at all). Going up/down stairs, driving, stressful events at work, home, and friend/family related stress were not statistically significantly associated with flares.” (Thomas et al. (2021))

However, besides these activity-related, psychosocial, and environmental triggers, the systematic review and meta-analysis by Wang et al. (2023) found that weather factors were significantly associated with pain in osteoarthritis. They found that barometric pressure (BP) and relative humidity (RH) were positively correlated with pain intensity based on their analysis of observational studies. 

“There was strong evidence that knee OA pain was influenced by meteorological factors as 3/4 of high-quality studies reported consistent findings. Temperature (T), relative humidity, and barometric pressure were the most frequent weather factors related to knee OA pain. There was moderate evidence that meteorological factors, especially barometric pressure, influenced hip OA pain.” (Wang et al. 2023)

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From: Wang et al., Ann Med. (2023)

Bongers and Vandenneucker (2020) examined weather conditions in people post-prosthetic surgery and found that barometric pressure, temperature, and humidity were correlated most with the worsening of pain in these people. But despite the correlations, no definite conclusions could be drawn. They stated that central sensitization mechanisms and cold hypersensitivity might play a role. 

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Xue et al. (2021) assessed 80 subjects and asked them if their symptoms of knee osteoarthritis were related to the weather. Of the participants, 42.5% reported no weather sensitivity, while 57.5% did report weather sensitivity. Upon further analysis of these 2 groups, the authors found significant differences in WOMAC pain scores, stiffness scores, function scores, and total scores in the ratio of quartile distribution between non-weather-sensitive and weather-sensitive participants. But, more importantly, they found differences in bone marrow and cartilage abnormalities between both groups. So it might be possible that weather-sensitive people have worse knee integrity status.

Schermafbeelding 2024 01 27 om 15.04.55

From: Xue et al., Rheumatol Ther. (2021)

But I hear you think, associations are not always causal, indeed. So we have to be cautious here and a possible explanation might lie elsewhere. One option might be that people move less in bad weather conditions. That was confirmed by a large study across six European countries (Timmermans et al. 2016). 

  • Higher temperatures were associated with increased outdoor physical activity
  • Increased humidity levels were associated with decreased outdoor physical activity
  • Temperature was more strongly associated with outdoor physical activity in people without osteoarthritis than in those with osteoarthritis.

How to measure?

Parry et al. (2018) found that the WOMAC and VAS are subjective tools frequently used in acute flare-ups in osteoarthritis. They can help define pain and symptoms of stiffness and difficulties in physical functioning. However, these questionnaires do not assess someone’s flare-up.

Here the Knee Osteoarthritis Flare-Ups Score (KOFUS) may help (Marty et al. 2009). 

Schermafbeelding 2024 01 27 om 15.33.08

From: Marty et al., Joint Bone Spine. (2009)

A patient-reported questionnaire that may aid in the evaluation of the severity of the flare from a patient’s perspective is the Flare-OA questionnaire (Traore et al. 2021).

Schermafbeelding 2024 01 28 om 16.05.16

From: Traore et al. Osteoarthritis Cartilage. (2022)

The list below may help you in choosing the right questionnaire to define flare-ups in osteoarthritis.

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From: Parry et al., BMJ Open (2018)

It is normal from time to time

Understanding how the symptom variability is related to the etiopathogenesis may be critical for long-term treatment. If some flare-ups are the joint’s response to mechanical load, there are two options:

  1. The associated inflammatory response could cause additional joint damage and  therefore the inflammation has to be stopped or reduced, 
  2. Or flare-ups are the joint’s attempt to restore homeostasis and are thus necessary after a bout of increased cartilage stress? 

If we had a better understanding of this process it could lead us to either focus on 1) decreasing the inflammation and prevention of the occurrence or 2) supporting the patient going through the inflammatory phase which may restore tissue homeostasis. 

Based on research by Lieberthal et al. (2015), this inflammatory response may also play a role in tissue repair, since besides the pro-inflammatory mediators, anti-inflammatory mediators are released, which allow for the resolution of inflammation and reduce the risk of progression of the injury. 

Explaining that flare-ups are common and may be distinct from true tissue damage might help to manage the uncertainty about symptom fluctuations. 

What does a flare-up mean from a patient’s perspective?

The research by Tollefsrud et al. (2020) examined the illness experiences of working-age individuals with osteoarthritis. They found that on average, people managed their daily activities and could live normal lives, but that unpredictable flare-ups and the feeling of losing control made their lives somewhat “fragile”. Physiotherapy can play an important role as we can guide these people to take back control of their lives. In our following blog, we will help you choose the right treatment to guide people experiencing flare-ups in osteoarthritis.

I hope you enjoyed reading this blog!

Ellen 🙂


Parry EL, Thomas MJ, Peat G. Defining acute flares in knee osteoarthritis: a systematic review. BMJ Open. 2018 Jul 19;8(7):e019804. doi: 10.1136/bmjopen-2017-019804. PMID: 30030311; PMCID: PMC6059300.

Parry E, Ogollah R, Peat G. ‘Acute flare-ups’ in patients with, or at high risk of, knee osteoarthritis: a daily diary study with case-crossover analysis. Osteoarthritis Cartilage. 2019 Aug;27(8):1124-1128. doi: 10.1016/j.joca.2019.04.003. Epub 2019 Apr 14. PMID: 30995523. 

Brandt KD, Dieppe P, Radin EL. Etiopathogenesis of osteoarthritis. Rheum Dis Clin North Am. 2008 Aug;34(3):531-59. doi: 10.1016/j.rdc.2008.05.011. PMID: 18687271.

Thomas MJ, Rathod-Mistry T, Parry EL, Pope C, Neogi T, Peat G. Triggers for acute flare in adults with, or at risk of, knee osteoarthritis: a web-based case-crossover study in community-dwelling adults. Osteoarthritis Cartilage. 2021 Jul;29(7):956-964. doi: 10.1016/j.joca.2021.04.007. Epub 2021 Apr 29. PMID: 33933585; PMCID: PMC8239447.

Wang L, Xu Q, Chen Y, Zhu Z, Cao Y. Associations between weather conditions and osteoarthritis pain: a systematic review and meta-analysis. Ann Med. 2023 Dec;55(1):2196439. doi: 10.1080/07853890.2023.2196439. PMID: 37078741; PMCID: PMC10120534.

Bongers J, Vandenneucker H. The influence of weather conditions on osteoarthritis and joint pain after prosthetic surgery. Acta Orthop Belg. 2020 Mar;86(1):1-9. PMID: 32490766. 

Xue Y, Chen Y, Jiang D, Wang L, Wang X, Li M, Wu Y, Zhang M, Pang J, Zhan H, Zheng Y, Ding D, Cao Y. Self-Reported Weather Sensitivity is Associated with Clinical Symptoms and Structural Abnormalities in Patients with Knee Osteoarthritis: A Cross-Sectional Study. Rheumatol Ther. 2021 Sep;8(3):1405-1417. doi: 10.1007/s40744-021-00340-w. Epub 2021 Aug 13. PMID: 34389921; PMCID: PMC8380616.

Timmermans EJ, van der Pas S, Dennison EM, Maggi S, Peter R, Castell MV, Pedersen NL, Denkinger MD, Edwards MH, Limongi F, Herbolsheimer F, Sánchez-Martínez M, Siviero P, Queipo R, Schaap LA, Deeg DJ; EPOSA research group. The Influence of Weather Conditions on Outdoor Physical Activity Among Older People With and Without Osteoarthritis in 6 European Countries. J Phys Act Health. 2016 Dec;13(12):1385-1395. doi: 10.1123/jpah.2016-0040. Epub 2016 Aug 24. PMID: 27633622; PMCID: PMC5384632.

Marty M, Hilliquin P, Rozenberg S, Valat JP, Vignon E, Coste P, Savarieau B, Allaert FA. Validation of the KOFUS (Knee Osteoarthritis Flare-Ups Score). Joint Bone Spine. 2009 May;76(3):268-72. doi: 10.1016/j.jbspin.2008.07.018. Epub 2009 Mar 17. PMID: 19297230.

Traore Y, Epstein J, Spitz E, March L, Maillefert JF, Rutherford C, Ricatte C, Alleyrat C, Cross M, King LK, Callahan LF, Fautrel B, Buttel T, Hawker G, Hunter DJ, Guillemin F. Development and validation of the Flare-OA questionnaire for measuring flare in knee and hip osteoarthritis. Osteoarthritis Cartilage. 2022 May;30(5):689-696. doi: 10.1016/j.joca.2021.12.011. Epub 2022 Jan 20. PMID: 35066175.

Lieberthal J, Sambamurthy N, Scanzello CR. Inflammation in joint injury and post-traumatic osteoarthritis. Osteoarthritis Cartilage. 2015 Nov;23(11):1825-34. doi: 10.1016/j.joca.2015.08.015. PMID: 26521728; PMCID: PMC4630675. 

Tollefsrud I, Mengshoel AM. A fragile normality – illness experiences of working-age individuals with osteoarthritis in knees or hips. Disabil Rehabil. 2020 Sep;42(18):2593-2599. doi: 10.1080/09638288.2019.1573930. Epub 2019 Mar 4. PMID: 30829074.

My goal is to deliver high-quality research findings in a highly accessible format for anyone interested in improving his or her knowledge and practical skills in the field of physiotherapy. Next to this, I want to critically review the evidence to keep you up to date with the most recent findings and stimulate you to improve your clinical thinking skills.
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