Abstract. Purpose. The aim of this study was to assess how biomechanical gait parameters (kinematics, kinetics, and muscle force estimations) differ between patients with camtype FAI and healthy controls, through a systematic search. Methods. A systematic review of the literature from PubMed, Scopus, and Medline and EMBASE via OVID SP was undertaken from inception to April 2020 using PRISMA guidelines. Studies that described kinematics, kinetics, and/or estimated muscle forces in cam-type FAI were identified and reviewed. Results. The search strategy identified 404 articles for evaluation. Removal of duplicates and screening of titles and abstracts resulted in full-text review of 37 articles with 12 meeting inclusion criteria. The 12 studies reported biomechanical data on a total of 173 cam-FAI (151 cam specific, 22 mixed type) patients and 177 healthy age, sex and BMI matched controls. Cam FAI patients had reduced hip sagittal plane ROM (Mean difference −3.00 0 [−4.10, −1.90], p<0.001), reduced hip peak extension angles (Mean Difference −2.05 0[−3.58, −0.53], p=0.008), reduced abduction angles in the terminal phase of stance, and reduced iliacus and psoas muscle force production in the terminal phase of stance compared to the control groups. Cam FAI cohorts walked at a slower speed compared to controls. Conclusions. In conclusion, patients with cam-type FAI exhibit altered sagittal and frontal plane kinematics as well as altered muscle force production during level gait compared to controls. These findings will help guide future research into gait alterations in FAI and how such alterations may contribute to pathological progression and furthermore, how such alterations can be modified for therapeutic benefit

To clarify the pathomechanisms of discogenic low back pain, the sympathetic afferent discharge originating from the L5-L6 disc via the L2 root were investigated neurophysiologically in 31 Lewis rats. Sympathetic afferent units were recorded from the L2 root connected to the lumbar sympathetic trunk by rami communicantes. The L5-L6 discs were mechanically probed, stimulated electrically to evoke action potentials and, finally, treated with chemicals to produce an inflammatory reaction. We could not obtain a response from any units in the L5-L6 discs using mechanical stimulation, but with electrical stimulation we identified 42 units consisting mostly of A-delta fibres. In some experiments a response to mechanical probing of the L5-L6 disc was recognised after producing an inflammatory reaction. This study suggests that mechanical stimulation of the lumbar discs may not always produce pain, whereas inflammatory changes may cause the disc to become sensitive to mechanical stimuli, resulting in nociceptive information being transmitted as discogenic low back pain to the spinal cord through the lumbar sympathetic trunk. This may partly explain the variation in human symptoms of degenerate discs.