The relationship between instability tests, pain and disability in non-specific low back pain.

Background and Objective. Clinical instability is considered one of low back pain (LBP) subgroups and can be recognized using tests evaluating lumbar stabilization during active or passive movements or measuring muscle endurance. Despite a recent systematic review confirmed that these tests may be recommended, at the current state of knowledge a complete investigation of their diagnostic accuracy is still needed. The aims of this study were: (1) to investigate the relationship between the clinical tests detecting spinal instability and the perceived pain and disability in non-specific low back pain (LBP); (2) to investigate the relationship between endurance and instability tests. Materials and Methods. 101 subjects (57.4% females, mean age 45.4 years) with non-specific LBP were included in this study from June to December 2014. Four instability tests [aberrant movements, active straight leg raising (ASLR), prone instability test (PIT), and passive lumbar extension test (PLE)], and two endurance tests [prone bridge test (PBT) and supine bridge test (SBT)] were performed by three physical therapists with expertise in orthopaedic manual therapy. Their results were compared with the Numerical Rating Scale and the Oswestry Disability Index, evaluating pain and disability, respectively. Results. AMs resulted positive in 55 subjects (54.7%), ASLR in 61 (60.4%), PIT in 35 (34.6%), and PLE in 39 (38.6%).The means (SD’s) for the PBT and for the SBT were 24.32 (25.92) and 81.46 (65.36), respectively. A low to moderate significant relationship between pain, disability and all tests but PBT was observed. A low to moderate significant relationship between instability tests and endurance tests was shown. The results of PBT and SBT were significantly related to the duration of symptoms (p-value = 0.0014; p-value = 0.0203, respectively). Discussion. Our data evidenced the existence of a significant relationship between disability and all clinical tests. A similar relationship was found with the amount of pain for all tests, with the exception of PBT. Conclusion. From a clinical point of view, more positive results on clinical instability tests may be expected in LBP subjects with higher level of disability or pain. The persistence of pain may significantly reduce anterior and posterior core muscles endurance