### Related Work
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Phase 1** & **Phase 2** & **Phase 3** \\ \hline
**Initial Rehabilitation Phase** & **Recovery Rehabilitation Phase** & **Intermediate–Final Rehabilitation Phase** \\
**(Duration: 2–6 weeks)** & **(Duration: 6–12 weeks)** & **(Duration: 12 weeks–1 year)** \\ \hline
**Achieve full range of knee** & & **One Rep Max (RM) single leg press** \\
**Achieve full range of knee** & & **Relative Strength Index (RSI) greater** \\
**extension to 120” flexion.** & & **then or equal to 125\%.** \\
**Minimal activity related** & **Bilaterally equal** & **Leg Symmetry Index (LSI) 85–100\% of knee extensors.** \\ joint effusion.** & & proprioception tests on single leg stance.** \\
**Reduce requirement for mobility aids as comfort, swelling, and knee control** & **Bilaterally equal strength of hamstrings, hip adductors, hip abductors, and gastrocnemius.** & **Symmetry on hop tests.** \\
**Achieve full range of knee** & & **Graded return to sport if set as patient** \\
**Achieve full range of knee** & & **goal, when patient has satisfied** \\
**Achieve full range of knee** & & **functional performance testing** \\
**Achieve full range of knee** & & requirements and when consultant has** \\
**Achieve full range of knee** & & **agreed for patient to return to sport.** \\
**Achieve full range of knee** & & **No contact sports for 6** \\
**Achieve full range of knee** & & **months post-operation.** \\
**Achieve full range of knee** & & **Establish long-term** \\
**Achieve full range of knee** & & **maintenance program.** \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Rehabilitation guidelines for patients undergoing ACL reconstruction rehabilitation. a system that utilized the existing architecture of Nintendo Wii Balance with the aim of improving balance controls to reduce the risk of falls in older patients. Feedback provided to the user was focused on positive reinforcement which occurred once the patient had completed an exercise. The benefits of this approach were that it allowed patients to understand when they had completed a task to the best of their ability. The key extrinsic motivational factor was the hope of improved quality of life from using the system. Their results showed a need to implement audible feedback; users stated that they would find this more stimulating and engaging. However, since basic ACLR rehabilitation exercises require the patient to remain in a specific position to ensure accurate knee angle detection, Wii platforms are not ideal for ACLR rehabilitation. Overall, gamification, like other persuasive architectures has merit, if implemented in the correct manner [12; 21]. However, current research has criticized gamification in the healthcare sector. For example, Deloitte [22] described gamification as 'just another over-glorified tech trend', while [PERSON] [23] considered it a quick fix adopted by innovators to increase and promote engagement. [PERSON] et al. [12] stated that these criticisms likely derive from the belief that \"features such as points and leader boards miss the essence and power of games as motivational techniques which have the potential to encourage behavior change or adherence to treatment programs positively\". Their study outlined the importance of encouraging engagement to treatment rather than technology, and that designers should consider this when applying gamification methods to contexts where the intention is to alleviate suffering and improve well-being [24]. To date, few studies have implemented gamification strategies to address rehabilitation requirements, specific to ACL reconstruction recovery. Therefore, the aim of this paper is to report the development of mobile system intervention capable of improving long-term post-operative outcomes for patients following ACLR surgery.