Longitudinal Changes in Lower Extremity Alignment and Mechanical Axis Parameters After Bariatric Surgery in Patients With Morbid Obesity: A Prospective Observational Study

Summary

The goal of this prospective observational study is to understand whether major weight loss after bariatric surgery is associated with changes in the alignment of the lower limbs in adults with morbid obesity.

The hips, knees, and ankles form a connected weight-bearing system that supports the body during standing and walking. The position of these joints in relation to one another affects how body weight and mechanical forces are transmitted through the legs. In people with severe obesity, increased body weight and changes in body shape may influence the way these forces are distributed across the lower extremities.

Bariatric surgery can result in substantial weight loss. However, it is not yet fully understood whether this degree of weight reduction is accompanied by measurable changes in the alignment of the hips, knees, and ankles or in the mechanical axis of the lower limbs.

This study will follow patients undergoing bariatric surgery and will evaluate them before surgery and again at approximately 3, 6, and 12 months after surgery. The study is observational. This means that researchers will observe and measure changes that occur during the patients' clinical course rather than assigning participants to a particular treatment for research purposes.

The main question is whether lower-extremity alignment and mechanical-axis measurements change during the first year after bariatric surgery as patients lose weight.

"Lower-extremity alignment" describes how the hip, knee, and ankle are positioned in relation to one another. The "mechanical axis" is an imaginary weight-bearing line used in orthopedics to describe how forces are transmitted through the leg from the hip toward the ankle. The position of this line in relation to the knee helps doctors understand how weight and mechanical forces are distributed across the lower limb.

Researchers will examine radiographic measurements that describe the overall relationship between the hip, knee, and ankle and the contribution of the thigh bone and shin bone to lower-limb alignment. Measurements obtained before bariatric surgery will be compared with those obtained at approximately 3, 6, and 12 months after surgery.

Following the same patients over several time points is important because weight loss after bariatric surgery occurs progressively rather than at a single moment. Repeated measurements will allow researchers to determine whether lower-limb alignment remains stable, changes early after surgery, changes gradually as weight decreases, or shows different patterns between individual patients.

The study will also explore whether the amount and course of postoperative weight loss are related to any observed changes in lower-extremity alignment.

The researchers do not assume that losing weight will automatically correct an existing bow-legged or knock-kneed appearance, or that every patient will show a measurable change in skeletal alignment. Some aspects of lower-limb alignment are determined by the shape and orientation of the bones and may remain stable. Other aspects of weight-bearing posture and the relationship between the joints may potentially change as body weight and body composition change. The purpose of this study is to objectively measure these changes rather than assume that they will occur.

Understanding the relationship between severe obesity, substantial weight loss, and lower-extremity alignment may be clinically important because mechanical loading is closely related to the function and health of the hip, knee, and ankle joints. Changes in lower-limb biomechanics may also be relevant to future research examining joint symptoms, osteoarthritis, walking mechanics, and orthopedic treatment planning.

The results of this study may therefore improve understanding of how the weight-bearing system of the lower limbs responds to major weight loss after bariatric surgery and may provide a scientific basis for further studies focusing on obesity and musculoskeletal health.

For patients and families, the study can be summarized simply as follows: the researchers want to find out whether losing a substantial amount of weight after bariatric surgery changes the way the legs line up from the hips through the knees to the ankles. Measurements obtained before surgery will be compared with measurements obtained at 3, 6, and 12 months after surgery. By observing the same patients throughout the first postoperative year, the researchers hope to understand whether weight loss changes the mechanical alignment of the lower limbs and, if changes occur, when they become measurable.

Conditions

• Obese
• Limb Deformities
• Arthritis

Interventions

OTHER

Obese.

Participants will undergo bariatric surgery as part of routine clinical care according to established clinical indications. The type of bariatric procedure will not be assigned or modified by the study. Participants will be prospectively followed, and lower-extremity alignment and mechanical-axis parameters will be evaluated using standing full-length lower-extremity radiographs before surgery and at approximately 3, 6, and 12 months after surgery. The study will assess longitudinal changes in hip-knee-ankle alignment and related femoral, tibial, and knee joint-line parameters during postoperative weight loss.

Sponsors & Collaborators

• Marmara University

  lead OTHER

Principal Investigators

• Muhammed F Serttaş, Medical Specialist, Consultant · Department of Orthopaedic Surgery and Traumatology, Marmara University, Pendik Training and Research Hospital, İstanbul, Turkey

Eligibility

Min Age

18 Years

Sex

ALL

Healthy Volunteers

No

Timeline & Regulatory

Start

2026-07-01

Primary Completion

2027-08-01

Completion

2027-08-01

Countries

• Turkey (Türkiye)

Study Locations