There is provided an apparatus (100) for detecting tissue inflammation. The apparatus (100) comprises a processor (102) configured to acquire, from at least one sensor (104), a plurality of photoplethysmography, PPG, signals indicative of light detected in a region of tissue at a plurality of respective locations within the region. The processor is also configured to process the acquired plurality of PPG signals to determine an amplitude and a phase of each of the plurality of PPG signals and detect tissue inflammation based on the determined amplitude and phase of each of the plurality of PPG signals.
