This is a descriptive retrospective study of individuals affected with knee osteoarthritis. The aim of this study is to describe the sociodemographic and clinical characteristics of individuals diagnosed with knee osteoarthritis within a specific health area, as well as to assess the economic impact of this condition on the healthcare system. To achieve this, medical records will be reviewed, and the following data will be collected:

Sociodemographic and clinical participant data. Healthcare resource use. Clinical burden. Up to 400 subjects will be enrolled in the Talavera de la Reina Health Area (Toledo, Spain).

This is a multicenter, observational, retrospective study focusing on individuals diagnosed with knee osteoarthritis. This study will be conducted in the Talavera de la Reina Health Area (Toledo, Spain). Participants will be identified through the codes assigned in the electronic database associated with knee osteoarthritis.

Data will be collected from the initial radiologic diagnostic moment to December 31, 2019. For each participant enrolled, data from medical records will be collected and entered onto an electronic case report form (REDCap).

The sociodemographic and clinical data related to the pathology will be collected, including age, weight, height, duration of the condition, and occupational activity.

The following data will be considered as direct healthcare costs: the number of visits in primary and specialized care, diagnostic tests, surgical interventions, and emergencies at both health centers and hospitals. In addition, pharmacotherapy, rehabilitation number of sessions, and work absences (temporary and permanent) will be registered.

For cost estimation, a prevalence-based approach and a bottom-up estimation will be employed in the monetary valuation of healthcare resources, utilizing official sources.

Inclusion Criteria:

• Patients ≥18 years old.
• Diagnosed with unilateral or bilateral knee osteoarthritis according to the clinical criteria of the American College of Rheumatology.
• Radiographic imaging diagnosis based on the Kellgren & Lawrence (K-L) classification.

Exclusion Criteria:

• No available X-ray.
• Pre-existing neurological diseases before the diagnostic date (stroke, Parkinson's, multiple sclerosis, ALS).
• Connective tissue disorders (Ehlers-Danlos, Marfan). Secondary cause of osteoarthritis or severe osteoarthritis (ACL tears, severe traumas, infections, or sepsis).
• Inflammatory arthropathy (any type of arthritis).
• Genetic disorders with a higher risk of developing arthropathies (Down syndrome).

Individuals with a diagnosis of knee osteoarthritis registered in the electronic database of Talavera de la Reina Health Area, Toledo, Spain.

Qualified researchers can request access to anonymized individual patient data to the IP researcher. All requests will be evaluated as the Talavera de la Reina Ethics Commitee.