Hip pain exacerbations are more likely to occur in people  with hip osteoarthritis who have episodes of hip bucking or ‘giving way’, an Australian study has found.

Hip ‘giving way’ as well as hip injury were identified as risk factors for episodes of unpredictable severe pain in a study of 252 patients with symptomatic hip OA conducted by researchers at the University of Sydney.

In an online-based study, researchers at Institute of Bone and Joint Research, Kolling Institute, monitored patients at 10 day intervals for 90 days through a series of questionnaires on pain  exacerbations and other hip events.

During the follow up period more than half the patients (n=133, 53%) had hip pain exacerbations, with a median number of 2.6 per patient.

Among this group of patients, 39% had a recent hip injury such as a fall or sports injury that limited their usual activity.  These results equated to a significantly increased risk (Odds Ratio 2.74) of hip pain exacerbation with injury compared to no injury.

Almost two thirds of patients with hip pain exacerbations reported (n=86, 65%) their hip giving way or buckling on at least one occasion during the follow up period. Recent hip ‘giving way’ (within the last two days) was associated with a significantly increased risk of hip pain exacerbation (OR 2.10), and there was a dose-response relationship between the number of buckling episodes and risk of hip pain.

Lead author Kai Fu, a PhD candidate in the Institute who co-authored the study in Arthritis Care & Research with rheumatologist Dr David Hunter, said the findings may provide some clues to the mechanisms of hip pain exacerbations in hip OA.

The association with recent hip injury may be explained by the release of inflammatory mediators triggering pain responses, and also activity-related pain, they suggested.

The link between pain fluctuations with hip ‘giving way’  were similar to those seen with knee joint instability and may be related to muscle weakness and lack of activity, they added.

“Lifestyle behavioural management strategies such as exercise and weight loss combined with proper medical treatment or psychological therapy are recommended for improving OA pain. There is also evidence showing that greater strength of the major hip and thigh muscles is associated with better self-reported physical function in patients with hip OA. Relevant muscle strengthening and balance training are potential ways to improve hip instability,” they wrote.