The Functional Muscle-Bone Incongruity Index (FKUI) is a novel approach developed to evaluate the relationship between muscle function and bone health. This prospective observational study aims to investigate the clinical applicability of FKUI, which combines handgrip strength, total hip bone mineral density (BMD), and lumbar-hip BMD discordance. Approximately 200 adult participants undergoing routine DXA assessment will be enrolled. The study will examine whether the combined evaluation of muscle function and bone health parameters provides a more comprehensive assessment of musculoskeletal status than individual measures alone.

This is a prospective, observational, single-center study evaluating adults undergoing routine DXA assessment in a Physical Medicine and Rehabilitation outpatient clinic. The study will investigate the clinical applicability of the Functional Muscle-Bone Incongruity Index (FKUI), a composite approach based on handgrip strength, total hip bone mineral density, and lumbar-hip bone mineral density discordance. No treatment or interventional procedure will be administered as part of the study. Handgrip strength will be measured using a calibrated hand dynamometer, and DXA-derived bone mineral density values will be recorded from routine clinical assessments. The study aims to determine whether the combined evaluation of muscle function and bone health parameters may provide a more comprehensive assessment of musculoskeletal status.

Inclusion Criteria:

• Age 18 years or older
• Attendance at the Physical Medicine and Rehabilitation outpatient clinic
• Scheduled to undergo routine bone mineral density assessment by DXA as part of clinical evaluation
• Ability to perform handgrip strength testing
• Availability of lumbar spine and total hip bone mineral density measurements suitable for analysis
• Ability and willingness to provide written informed consent

Exclusion Criteria:

Exclusion Criteria:

• Age younger than 18 years
• Secondary causes of osteoporosis (e.g., hyperparathyroidism, Cushing syndrome, malignancy, or other conditions affecting bone metabolism)
• History of metabolic bone disease
• Major trauma or fracture within the previous 6 months
• Upper extremity disorders that may significantly affect handgrip strength measurement (e.g., severe osteoarthritis, neurological disorders, major deformities)
• DXA measurements that are technically inadequate or unsuitable for analysis
• Refusal or inability to provide written informed consent

The study population will consist of adults aged 18 years and older attending the Physical Medicine and Rehabilitation outpatient clinic who are scheduled to undergo routine dual-energy X-ray absorptiometry (DXA) assessment as part of their clinical evaluation. Participants will be recruited consecutively from routine clinical practice. The study aims to evaluate the relationship between muscle function and bone health through the Functional Muscle-Bone Incongruity Index (FKUI), which incorporates handgrip strength, total hip bone mineral density, and lumbar-hip bone mineral density discordance.

No plan has been established to share individual participant data. Participant confidentiality will be maintained in accordance with ethical and institutional requirements.