Lower-limb rehabilitation exoskeletons have arisen as effective instruments for aiding patients with mobility issues in their recovery process and addressing the difficulties encountered by physical therapists, such as staff shortages and the physically demanding nature of repetitive sessions. Nonetheless, research has also shown that patients frequently develop a reliance on the passive assistance provided by such devices, which may result in a decline in the yield that can be acquired from rehabilitation training sessions. With this, the study highlights the development of a wearable exoskeleton for active-assist knee flexion-extension that can be adaptable and work in conjunction with other existing rehabilitation devices for knee movement. This system provides emphasis on the principle of effort, which in return results in the objective of the study in detecting motion intention and angle change for a period of every 100 milliseconds. Based on the obtained values, a control signal with knee flexion or knee extension as output would be provided if and only if the developed exoskeleton detects motion intention from the user but no change in angle was produced—denoting that the user’s strength may not be enough to perform the intended action. This ensures the active participation of patients in their physical therapy sessions. Allowing for a mechanical input rather than utilizing physiological signals revealed great potential in reducing the risk of acquiring noisy data. Experimental results show that the developed exoskeleton has achieved a classification accuracy of at least 90% for detecting changes in angle and motion intention.