Submitted in partial compliance with the requirements for the Master’s Degree in Technology: Chiropractic, Durban University of Technology, 2014. / Aim: To determine the effect of long axis manipulation of the third metacarpophalangeal joint (MCP) on articular surface separation, peri-articular soft tissue movement and joint cavitation. Participants: Forty two right-handed healthy individuals between 18 and 28 years of age from the Durban University of Technology campuses, KwaZulu Natal. Methodology: Written informed consent was obtained from each participant. A case history, physical examination and a hand and wrist orthopaedic assessment was conducted for each participant. Study specific data, such as sex, age, height and weight were recorded. A diagnostic ultrasound (US) scan was done to the left third MCP joint for each participant while distractive manipulation was applied to the joint. The presence or absence of audible release was noted and the tension levels applied to the joint was measured with a digital tension meter. Joint surface separation (JSS), synovial membrane position (SMP), gas bubble presence and location were assessed on the US recordings at baseline, just prior to cavitation, at maximum traction and in the post-traction resting joint. IBM SPSS version 20 was used to analyse the data. Independent sample t-tests were used to compare the means between the two groups and the associations were compared using Pearson’s chi square tests. A p value <0.05 was considered as statistically significant. Results: Long axis manipulation resulted in audible release in 22 of the participants (Group and no audible release in 20 of the participants (Group 2). No significant difference in joint surface separation or the synovial membrane position could be established between MCP joints that cavitated and MCP joints that did not cavitate at the baseline, as well as in maximum traction and in the post-procedure resting joint (p > 0.05; t-test). Hyperechoic gas bubbles were present in 21 of the 22 participants of Group 1 and no gas bubbles could be visualised in the participants in Group 2. The presence of intra-articular hyperechoic gas bubbles was highly associated with audible release (p < 0.001; Pearson’s chi square test). Due to the predefined features of cavitation, gas bubble inception was could not be detected in the Group 1 participants prior to cavitation. In Group 1, 95.5% of the gas bubbles were present in the middle third of the joint at maximum traction. At the post traction resting joint evaluation, no gas bubble was evident in 42.9% (n = 9) of the joints; 42.9% (n = 9) indicated bubbles were present only in the dorsal third, whilst 9.5% (n = 2) presented bubbles in the middle and dorsal third; and in one case gas bubbles were seen in the dorsal, middle and ventral thirds of the joint space. The mean manipulative force recorded in participants in which gas bubble inception took place during manipulation was 5.7 kg, and in those with no gas bubble inception was 12 kg. There was a significant difference between the mean traction force applied to those with and to those without a gas bubble appearance (p < 0.001; t-test). Conclusion: No significant differences were observed between the cavitation and non-cavitation groups for the joint surface separation and synovial membrane movement at various stages of manipulation. A significant association was established between the audible release of a joint that was manipulated and the appearance of intra-articular gas bubbles or micro-bubbles. The mean traction force that was required to cause cavitation was significantly lower than the force to which joints with no cavitation were tensioned. The findings concur with those of previous studies that cavitation is a necessary component of joint manipulation.