Isometric quadriceps pressure difference: A simple and cost-effective tool to identify and regain quadriceps muscle strength following anterior cruciate ligament reconstruction - A case series

Introduction: Quadriceps weakness and extension deficit of the knee following anterior cruciate ligament (ACL) reconstruction (ACLR) can threaten rehabilitation, and isometric quadriceps exercise is the usual prescription. However, the outcome depends more on the individual's re-learning process. Identification of this lacuna and focussed attention to the isometric strength of quadriceps are lacking in the current practice, and developing a tool can lead to optimal outcomes in ACLR. The objective of this study was to assess the role of 'isometric quadriceps pressure difference' (IQPD) in regaining quadriceps strength following the ACLR using a simple tool. Patients and Methods: Eight patients who underwent post-operative ACL rehabilitation between March 2016 and May 2018 were analysed retrospectively. A 'progressive isometric training protocol (PITP)' based on IQPD was prescribed along with the standard protocol. Data were collected from the case records of the patients. IQPD, thigh muscle girth and heel height difference (HHD) were noted pre-operatively, immediately following surgery and 3 months post-operatively. A non-parametric test was used to compare the outcomes before and after surgery. Results: Based on the analysis, the inclusion of IQPD-based PITP in regaining the terminal extension had a significant statistical difference in the IQPD, HHD and girth (p < 0.007, p < 0.005 and p = 0.027, respectively). Conclusion: IQPD can be a simple, cost-effective strategy to identify subtle quadriceps weakness. Further, PITP can improve the isometric quadriceps strength in the acute post-operative period and reduce the incidence of knee extension deficit in post-ACLR.