Association Between the Acquired Functioning and Personal Satisfaction After Total Knee Arthroplasty: A Study Based on a Classification and Regression Tree

Introduction

Osteoarthritis (OA) is the most common musculoskeletal condition and is characterized by multiple impairments of structures and functions, progressing to joint damage that, over time, becomes irreversible, significantly impacting individuals’ performance of activities and quality of life. In the case of knee OA, the most common manifestations comprise pain, stiffness, loss of mobility, and disability in activities of daily living, for which the standard surgical treatment in the terminal phase is total knee arthroplasty (TKA).About 33.6% of the population aged 65 and older suffer from OA (Lawrence et al., 2008), whose risk to the knee is lifelong; when comparing men and women, 40 and 47%, respectively, are affected by this comorbidity, whose effects are exacerbated by obesity (Neogi & Zhang, 2013). The pathophysiology of OA is complex and includes mechanisms of cellular stress and degradation of the extracellular matrix, with maladaptive responses from innate immunity and significant repercussions at the cartilage level and in other joint structures, including subchondral bone, menisci, ligaments, synovial membrane, and synovial fluid (Brandt et al., 2006). The higher prevalence of OA in females is related to hormonal physiology and anatomical specificities. Genes that code for estrogen receptors increase the risk of OA, and women have thinner articular cartilages, a Q angle that is about 3° higher than men, a narrower and shorter distal femur, and a difference in the size of the tibial plates (Hitt et al., 2003).

Obesity is commonly associated with hip and knee OA due to the implicit overload it causes these joints. However, other justifications for its association are related to biological mechanisms, such as cartilage growth and bone factors, whose higher presence in obesity precipitates joint degradation (Felson, 1992). Another factor related to knee OA is traumatic injuries throughout the life cycle, specifically those involving the menisci and anterior cruciate ligament. A meniscal lesion or partial meniscectomy tends to potentiate the onset of OA due to the close kinematic relationship between the menisci and articular cartilage (Madry et al., 2012). Nevertheless, Ajuied et al. (2014) reported that anterior cruciate ligament injuries increase the risk of knee OA by 3.89 due to the instability they cause in this joint by changing the load-bearing area to the periphery, thus overloading the articular cartilage in this region (Heijink et al., 2012).

Total knee arthroplasty is one of the most performed musculoskeletal surgeries and is considered a highly effective intervention. It provides overall good functional results and high satisfaction levels. In the last decade, TKAs have increased exponentially due to the aging population, increased prevalence of obesity, and leisure activities (Murphy & Helmick, 2012; United States Bone and Joint Initiative, 2014). Despite providing high levels of satisfaction, various studies have reported that 20–30% of patients are dissatisfied, with surgeons curiously expressing higher levels of satisfaction with the results obtained compared to patients (Bourne et al., 2010; Canovas & Dagneaux, 2018; Dunbar et al., 2013; Gunaratne et al., 2017; Khatib et al., 2020).

Although numerous factors influence patient satisfaction, one of the main reasons for dissatisfaction is high patient expectations. When these patients do not achieve the expected results, they may be ten times more likely to be dissatisfied with their treatment outcome (Canovas & Dagneaux, 2018). However, these expectations relate to pain relief, improved physical capacity, and improved psychosocial well-being. Other factors contributing to dissatisfaction include demographic factors such as age and sex and functional factors such as residual pain, stiffness and inflammation, low postoperative functional capacity, and postoperative complications (Bourne et al., 2010; Canovas & Dagneaux, 2018).