Background: Lower limb osteoarthritis (OA) causes high levels of individual pain and disability and is an increasing socio-economic burden to global healthcare systems. Physical Activity interventions are commonly provided by physiotherapists to help patients with lower limb OA manage their clinical symptoms. Objective: To identify and evaluate the effectiveness of behavioural change techniques (BCTs) within physiotherapy interventions to increase physical activity (PA) adherence in patients with lower limb OA. Design: A systematic review was conducted, following Cochrane guidelines according to a published and registered protocol (CRD42016039932). Two independent researchers conducted searches, determined eligibility, assessed risk of bias (Cochrane tool), intervention fidelity (NIHBCC checklist), and coded randomised controlled trials (RCTs) for BCTs (V1 taxonomy). BCT effectiveness ratios were calculated and RCT risk of bias and intervention fidelity were summarised narratively. Data sources: A highly sensitive search strategy was conducted on Medline, Embase, PsycINFO, CENTRAL, CINAHL and PEDro and grey literature databases from inception to January 2nd, 2018. Reference lists of included RCTs and relevant articles were reviewed, and a citation search was conducted using Web of Science. Eligibility criteria for selecting studies: RCTs that evaluated the effectiveness of a physiotherapy intervention that incorporated >1 BCT that promoted home or community-based PA adherence in patients with lower limb osteoarthritis. Results: Twenty-four RCTs (n = 2366 participants) of variable risk of bias (RoB) (5 low; 7 moderate; 12 high) and poor intervention reporting from 10 countries were included. Heterogeneity of intervention BCTs and PA adherence outcome measures precluded meta-analysis. Thirty-one distinct BCTs were identified in 31 interventions across RCTs. In general, BCTs demonstrated higher effectiveness ratios for short-term and long-term PA adherence compared with medium-term outcomes. The BCTs ‘behavioural contract’, ‘non-specific reward’, ‘patient-led goal setting’ (behaviour), ‘self-monitoring of behaviour’, and ‘social support (unspecified) demonstrated the highest effectiveness ratios across time points to promote PA adherence. Conclusions BCTs demonstrate higher short and long-term than medium-term effectiveness ratios. Further research involving low RoB RCTs incorporating transparently reported interventions with pre-specified BCTs aimed at optimising lower limb OA patient PA adherence is required.