A clinical observation on sciatica conducted by the School of Chinese Medicine (SCM) revealed that 86.29% of the cases resulted from the dislocation of sacroiliac joint whereas only 7.26% of the cases are related to lumbar disc protrusion. Prior to this study, lumbar disc protrusion was commonly considered to be the clinical casual factor for this problem.

Dislocation of sacroiliac joint is also known as dislocation of the pelvis. People who sit or stand for long periods, as well as those who perform excessive heavy manual labour are prone to sciatica. Mr Sun Feng, Senior Lecturer of the Clinical Division of SCM, conducted a clinical observation on 248 sciatica patients who attended medical consultations during the period from March 2008 to January 2015 at HKBU Chinese medicine clinics and some clinics run by members of the Hong Kong Traditional Chinese Medicine Orthopaedic and Traumatic Association. The 94 male and 154 female patients, with ages ranging from 16 to 77, have been suffering from pain for a period of 2 hours to 20 years.

The 248 patients were physically examined in accordance with the diagnostic standards for “lumbar disc protrusion”, “dislocation of sacroiliac joint” and “spinal compression”. It was found that 214 of the patients (86.29%) experienced pain due to “dislocation of sacroiliac joint”; nine of them (3.63%) had the symptoms of both “lumbar disc protrusion” and “dislocation of sacroiliac joint” at the same time; 18 of the cases (7.26%) encountered the problems of “lumbar disc protrusion” while the remaining seven patients (2.82%) were suffering from “spinal compression”. The observation pointed to a relationship between sciatica and dislocation of pelvis.

In elucidating the relationship between dislocation of sacroiliac joint and sciatica, Mr Sun Feng said that the dislocation would give rise to unequal leg length which would further aggravate the condition of the joints connecting the kinematic chain of pelvic, hip, knee and ankle. At the same time, the thirty-odd groups of muscles and tendons responsible for maintaining pelvic stability would also lose balance, resulting in stretch and compression of  the sciatic nerves running along the affected areas, thereby causing sciatic pain from the waist and hip extending to the legs. Severe cases may result in foot paralysis.

The present observation is a further analysis of a statistical analysis conducted by Mr Sun Feng on Hong Kong Chinese medicine out-patient lumbocrural pain occurrence. In that statistical analysis, it was found that patients who were suffering from sacroiliac joint dislocation also experienced pelvic pain, knee pain, ankle pain, sciatica or paralysis, frequent micturition or abdominal pain. Often, patients incorrectly consult doctors on these symptoms instead of looking into the causal factor. Mr Sun suggested that medical practitioners should conduct physical examination on sacroiliac joint with a view to provide appropriate therapy for patients.