Fukuoka, Japan—Total hip arthroplasty (hip replacement) is a common treatment for hip osteoarthritis, a degenerative joint disease caused by cartilage in the hip joint wearing down. However, clinical outcomes vary between patients, and the best timing for surgery remains unclear.
Now, researchers at Kyushu University have identified that pre-surgery walking speed is a strong predictor of post-surgery outcomes. In a study published on 26 November in The Journal of Bone and Joint Surgery , they found that patients who could walk at least 1 meter per second (m/s) before surgery were significantly more likely to report good postoperative results.
"Among all the factors we examined, gait speed stood out as the most consistent and reliable predictor of better recovery," says first author, Dr. Yuki Nakao, a medical doctor and PhD student in the Department of Orthopaedic Surgery and the Graduate School of Medical Sciences . "Its simplicity also makes it a practical measure that clinicians can easily incorporate into their routine preoperative assessment."
Osteoarthritis, which is the most common form of arthritis, is a growing issue that affects more than 500 million people worldwide. It often causes severe pain and joint stiffness and significantly impacts quality of life. For hip osteoarthritis, total hip arthroplasty, where surgeons replace the damaged joint with an artificial one, is an effective but last-resort treatment. However, determining the right time for surgery remains difficult. Doctors typically rely on factors such as pain intensity or the severity of osteoarthritis as assessed by hip X-rays, but research has been inconclusive about whether these criteria reliably predict good postoperative outcomes.
To address this gap, Nakao and colleagues, including Associate Professor Satoshi Hamai and Professor Yasuharu Nakashima from the Faculty of Medical Sciences , aimed to identify preoperative factors that could predict mid-term, patient-reported outcomes 5–10 years after surgery.
The researchers analyzed data from 274 patients who underwent total hip arthroplasty for osteoarthritis at Kyushu University Hospital between 2012 and 2018. All patients completed detailed physical assessments the day before surgery, including measurements of pain level, the hip's range of motion, lower-limb muscle strength, and a 10-meter walking test. In August 2023, these patients then answered two standardized post-questionnaires: the Oxford Hip Score, which assesses pain and hip function; and the Forgotten Joint Score-12, which measures the patient's awareness of their hip joint and level of discomfort.
To determine which patients had achieved a meaningful recovery, the research team used established Patient Acceptable Symptom State (PASS) thresholds. Patients who scored at least 42 points on the OHS and at least 50 points on the FJS-12 were considered satisfied with their surgical outcome.
The researchers then analyzed their outcomes against 15 different factors, including their age at surgery, sex, BMI, duration of symptoms, length of follow-up period, and severity of osteoarthritis based on preoperative hip X-rays. They also used the physical assessments measured on the day before surgery, including the 10-meter gait speed test.
"While we saw a few significant factors emerge for each questionnaire in isolation, gait speed was the only significant factor across both questionnaires, highlighting its reliability," says Nakao.
To gain deeper insight, the team also used machine learning to group patients into three clusters based on their questionnaire responses: those with excellent, moderate, and poor outcomes.
When the researchers looked at which factors best predicted an excellent outcome, walking speed was the only significant predictor, with a gait speed of about 1.0 m/s marking the key threshold separating those with excellent recovery from everyone else.
Although the research has limitations as it can only identify associations rather than causes, gait speed's strength and reliability as a predictor of surgery success, along with how easy it is to measure, make walking tests a promising tool for future clinical practice. Gait speed could help physicians determine when to refer patients for surgery, and preoperative rehabilitation programs could be developed to help patients reach a walking speed of at least 1.0 m/s.
"We hope that bringing this knowledge into clinical practice will support better recovery and ultimately improve outcomes for patients undergoing hip replacement surgery," Naoko concludes.
