Gender Disparities in Knee Pain Prevalence

June 3, 2024

Unveil the gender differences in knee pain prevalence, risk factors and the role of central sensitivity.

Understanding Gender Disparities in Knee Pain Prevalence

Women are more likely to report knee pain than men, with studies finding a higher prevalence of knee pain in women across all age groups.
The gender gap in knee pain prevalence widens with increasing age, with women over 50 being significantly more affected than men in the same age group.
Women are more likely to develop knee osteoarthritis, with some studies suggesting a 2-3 times higher risk compared to men.
The lifetime risk of symptomatic knee osteoarthritis is estimated to be 40% in men and 47% in women.
Women tend to report more severe knee pain and greater functional limitations compared to men with the same radiographic severity of knee osteoarthritis.
The prevalence of knee pain in women is consistently higher than in men across different countries and cultures, suggesting a biological basis for the gender disparity.
Women are more likely to seek medical attention for knee pain and to use pain medications compared to men.
The gender difference in knee pain prevalence is not fully explained by differences in body mass index, physical activity levels, or hormonal factors.
Women with knee osteoarthritis are more likely to undergo total knee replacement surgery than men, possibly due to greater pain severity and functional limitations.
The higher prevalence and severity of knee pain in women highlights the need for gender-specific approaches to prevention, diagnosis, and treatment of knee disorders.

Gender Disparities in Knee Pain

Investigating the presence of gender differences in knee pain prevalence, multiple studies have found that women tend to report greater knee pain than men, a discrepancy that persists across varying degrees of knee damage.

Pain Severity Discrepancy

In studies, women have reported higher Visual Analog Scale (VAS) pain scores at all Kellgren and Lawrence (KL) grades - a scale used to classify the severity of osteoarthritis. This difference in pain severity was observed in both unadjusted analyses and those adjusted for various covariates, including widespread pain (WSP).

Gender	VAS Pain (unadjusted)	VAS Pain (adjusted)
Women	Higher at all KL grades	Significant for KL grade ≤2 and 2
Men	Lower at all KL grades	Less significant for KL grade ≤2 and 2

These differences were generally small but became more pronounced in the presence of Patellofemoral Osteoarthritis (PFOA), a specific type of knee osteoarthritis that affects the front of the knee [1].

Impact of Patellofemoral Pain

In cases of PFOA, women reported greater pain severity for all KL grades in both unadjusted and adjusted analyses. This suggests that PFOA may exacerbate the already observed differences in pain severity between men and women [1].

PFOA Impact	Women	Men
Greater Pain Severity	Yes, at all KL grades	No, less significant at all KL grades

Even after adjusting for all covariates, women consistently reported greater or equal knee pain compared with men at each KL grade. The differences were more significant for KL grades below 4 [1].

The strong association between pain severity and the presence of widespread pain suggests that central sensitivity may be one component contributing to the observed sex differences in knee pain severity.

In conclusion, the evidence points to a clear gender disparity in the prevalence and severity of knee pain, with women reporting greater pain than men. This highlights the need for further research and tailored interventions to effectively manage knee pain in both genders.

Prevalence of Knee Pain

Underlining the gender differences in knee pain prevalence, it's crucial to explore studies conducted in different regions of the world. This section will focus on two such studies carried out in Saudi Arabia and China.

Study in Saudi Arabia

In Saudi Arabia, a study found notable differences in the prevalence of Patellofemoral Pain (PFP) among males and females. The overall prevalence of PFP among the study participants was found to be 30.3%, with a slightly higher prevalence among males (31.4%) compared to females (29.5%).

Gender	Prevalence of PFP
Male	31.4%
Female	29.5%

In addition to PFP, the study also revealed that the prevalence of knee pain among the participants was 13.2%, with 14% prevalence among males and 12.3% prevalence among females.

Gender	Prevalence of Knee Pain
Male	14%
Female	12.3%

Study in China

A similar study conducted in China found that Patellofemoral Pain (PFP) was present in 20.7% of participants, and knee discomfort was prevalent in 35.6% of participants, with no significant link to gender, age, or body mass index.

Condition	Prevalence
PFP	20.7%
Knee Discomfort	35.6%

These studies provide valuable insights into the prevalence of knee pain and Patellofemoral Pain among different genders. As research continues, it's essential to keep exploring these disparities to better understand the risk factors and develop effective treatment strategies.

Risk Factors for Knee Osteoarthritis

Knee osteoarthritis is a common ailment, particularly in older populations. However, the risk factors for developing osteoarthritis are not equally distributed across genders. This section delves into the gender differences in risk factors and explores the impact of body mass index (BMI) and age on knee osteoarthritis prevalence.

Gender Differences in Risk Factors

The prevalence of risk factors for knee osteoarthritis tends to be higher in women compared to men, with a few exceptions such as alcohol intake and smoking, which are higher in men. However, a high body mass index shows an equal prevalence among both genders. Sex-specific differences are found in risk estimates for knee osteoarthritis, with a higher level of physical activity and a Kellgren and Lawrence score of 1 at baseline being more prevalent in men. Meanwhile, a BMI ≥27 is associated with a higher risk for knee osteoarthritis in women.

Risk Factor	Women	Men
Alcohol Intake	Lower	Higher
Smoking	Lower	Higher
BMI ≥27	Higher Risk	Lower Risk
High Level of Physical Activity	Lower	Higher
Kellgren and Lawrence Score 1	Lower	Higher

Impact of BMI and Age

Obesity has a greater impact on knee osteoarthritis in women compared to men, with the risk for radiographic knee osteoarthritis being significantly higher in women with a BMI ≥27 compared to men. The population attributable fraction for higher BMI is 25.6% in women and 19.3% in men, indicating a strong link between obesity and knee osteoarthritis.

After the age of 50, the incidence of knee osteoarthritis in women increases steeply compared to men, leading to a higher prevalence in women. Furthermore, knee osteoarthritis in women is often accompanied by greater pain and disability compared to men.

Factor	Women	Men
Age (Above 50)	Higher Incidence	Lower Incidence
Obesity (BMI ≥27)	Higher Risk	Lower Risk

These findings emphasize the importance of considering gender differences in knee pain prevalence while devising strategies for prevention and treatment. Further research is needed to understand the underlying mechanisms that lead to these disparities.

Knee Osteoarthritis in Women

When it comes to knee osteoarthritis (OA), gender differences are significant. Women are more likely to suffer from this condition, and their experiences tend to be more severe compared to men.

Higher Prevalence and Severity

Women with OA have a higher prevalence rate, experience more clinical pain, inflammation, and physical difficulty, and have smaller joint parameters and dimensions compared to men. This gender difference becomes more pronounced after the age of 50 and increases dramatically around the time of menopause. Women also lose articular cartilage from the proximal tibia at four times the annual rate of men and from the patella at three times a greater rate.

In patients with knee OA who undergo total knee arthroplasty, women have lower functional scores and report greater pain than men both before and after the operation. In a study of 5290 patients two years after surgery, 36% more women than men reported moderate to severe pain. Even after accounting for age and preoperative pain level, women were more likely to have moderate-to-severe pain at 2 years after arthroplasty.

Factors that contribute to the persistence of chronic pain after total knee replacement in patients with OA include high pain ratings prior to surgery, high pain ratings in the immediate postoperative period, multiple pain sites, loss of central inhibition preoperatively, higher pain catastrophizing, and the sex of the individual, with women at greater risk of chronic pain after surgery [5].

Treatment Disparities

Women with knee OA are more likely to use health care resources, consult orthopedic surgeons, be on waiting lists for total hip replacement, and receive various treatments such as analgesics, injections, imaging, and physical therapy compared to men.

However, it's important to note that differences between men and women with osteoarthritis are complicated by the fact that women may also be pre- or post-menopausal. Post-menopausal women may also be undergoing replacement therapy. These factors are rarely considered in the analysis and determination of factors that contribute to differences in pain and function in osteoarthritis [5].

The nuances in the experience of women with knee OA underline the importance of gender-specific research and treatment strategies. Establishing a more comprehensive understanding of the gender disparities in knee pain prevalence can help shape more effective and personalized treatment plans.

Central Sensitivity and Pain

As we delve deeper into the understanding of gender differences in knee pain prevalence, it's crucial to consider the role of central sensitivity and pain-related factors. These include the role of the central nervous system and the influence of psychological factors on pain perception.

Role of Central Nervous System

Pain is a complex phenomenon, created and modulated by the central nervous system (CNS). The CNS manages the experience of pain, whether it originates from nociceptive input (e.g., knee arthritis) or is maintained independent of such input. Pain is the result of a dynamic balance between facilitation and inhibition of information processing. In individuals with chronic osteoarthritis (OA), there is increased central excitability and decreased central inhibition [5].

Central excitability can be assessed by testing "temporal summation," which corresponds to a progressive increase in reported pain in response to the same noxious stimulus given repetitively. Studies have shown that people with OA show augmented temporal summation to noxious stimulation compared with controls. Furthermore, temporal summation among individuals with osteoarthritis is greater in those with higher pain than in those with lower pain. Additionally, temporal summation significantly correlates with other aspects of OA pain, such as pain duration and pain during walking, suggesting central excitability may underlie these pain measures as well.

Psychological Factors in Pain

Pain is not merely a physical sensation; it's a multidimensional experience that encompasses psychological, emotional, environmental, and social factors. While the literature on environmental and social factors related to sex differences in OA pain is limited, it's evident that psychological and emotional factors play a significant role in pain perception and management.

There is a wide variation in how individuals cope with pain, how they interpret and report pain, as well as how psychosocial and environmental factors influence their pain experience. Understanding these factors is vital in managing chronic pain conditions like OA, especially considering the observed gender disparities in knee pain prevalence.

These insights into the role of central sensitivity and psychological factors further emphasize the complex nature of pain and the need for a comprehensive approach to pain management. It also highlights the necessity for research and interventions that recognize and address the gender differences in the experience and management of knee pain.

Predictive Factors for Chronic Pain

Understanding the factors that predict chronic pain, especially after surgical interventions like total knee replacement, is crucial in managing and treating knee pain effectively. A clear understanding of these factors can help tailor treatment plans and manage patient expectations, particularly in populations at higher risk, such as women.

Post-Surgery Pain Risk

Chronic pain after knee surgery, particularly total knee replacement, can be influenced by several factors. High pain ratings prior to surgery, elevated pain ratings in the immediate postoperative period, multiple pain sites, loss of central inhibition preoperatively, high pain catastrophizing, and gender, with women being at increased risk, are all associated with the persistence of chronic pain after total knee replacement in patients with osteoarthritis.

Sex-Specific Considerations

Differences in pain experience between men and women with osteoarthritis can be complicated by factors such as menopausal status. For instance, post-menopausal women may be undergoing replacement therapy, which can potentially influence pain and function outcomes in osteoarthritis. Unfortunately, these factors are rarely considered in the analysis and determination of factors contributing to differences in pain and function in osteoarthritis [5].

Pain is a multifaceted experience that encompasses psychological, emotional, environmental, and social factors. Individuals vary in their coping mechanisms, perceptions, and reporting of pain, as well as in the psychosocial and environmental factors influencing their pain. Unfortunately, literature on environmental and social factors related to gender differences in osteoarthritis pain is limited, although there is a growing body of research focusing on social factors related to knee osteoarthritis surgery.

Pain is a product of the central nervous system (CNS), which creates and modulates the experience of pain. In people with chronic osteoarthritis, there is increased central excitability and decreased central inhibition. Central excitability can be assessed by testing “temporal summation,” which corresponds to a progressive increase in reported pain in response to the same noxious stimulus given repetitively. People with osteoarthritis show augmented temporal summation to noxious stimulation compared with controls, and temporal summation among people with osteoarthritis is greater in those with higher pain than in those with lower pain (> 6 VAS vs. <6 VAS). In addition, temporal summation significantly correlates with other aspects of osteoarthritis pain, such as pain duration and pain during walking, suggesting central excitability may underlie these pain measures as well.

These findings highlight the importance of incorporating sex-specific considerations in the diagnosis, management, and treatment of knee osteoarthritis to address the gender differences in knee pain prevalence effectively.