A locking mechanism of an armrest assembly for a wheelchair, comprising: an elongated inner arm having a pivot end portion configured to be pivotally attached to a seating system frame of the wheelchair, and a first elongated body extending from the pivot end portion, an elongated outer profile having a proximal outer profile end face provided with an axially extending channel configured to receive the first elongated body, and a distal outer profile end portion, the outer profile being configured to move linearly relative to the inner arm, between a proximal position relative to the pivot end portion and a distal position, a locking handle having a second elongated body configured to receive the outer profile, the locking handle having a proximal locking handle end portion relative to the pivot end portion of the inner arm and a distal locking handle end portion, the distal locking handle end portion being configured to be pivotally attached to the distal outer profile end portion thereby forming a first pivot connection, wherein the locking handle is configured to pivot about the first pivot connection relative to the outer profile and the inner arm, between a proximal pivot position and a distal pivot position in which the locking handle is pivoted further away from the outer profile than in the proximal pivot position, and a locking structure, wherein when the outer profile is in the proximal position and the locking handle is moved to the distal pivot position, the locking handle is configured to cause the locking structure to engage with the outer profile and the inner arm to axially interlock the outer profile with the inner arm, and wherein the locking handle is configured to move the locking structure from engagement with the outer profile and the inner arm to release the outer profile from axial interlocking with the inner arm when the outer profile is in the proximal position and the locking handle is moved from the distal pivot position towards the proximal pivot position. an elongated inner arm having a pivot end portion configured to be pivotally attached to a seating system frame of the wheelchair, and a first elongated body extending from the pivot end portion, an elongated outer profile having a proximal outer profile end face provided with an axially extending channel configured to receive the first elongated body, and a distal outer profile end portion, the outer profile being configured to move linearly relative to the inner arm, between a proximal position relative to the pivot end portion and a distal position, a locking handle having a second elongated body configured to receive the outer profile, the locking handle having a proximal locking handle end portion relative to the pivot end portion of the inner arm and a distal locking handle end portion, the distal locking handle end portion being configured to be pivotally attached to the distal outer profile end portion thereby forming a first pivot connection, wherein the locking handle is configured to pivot about the first pivot connection relative to the outer profile and the inner arm, between a proximal pivot position and a distal pivot position in which the locking handle is pivoted further away from the outer profile than in the proximal pivot position, and a locking structure, wherein when the outer profile is in the proximal position and the locking handle is moved to the distal pivot position, the locking handle is configured to cause the locking structure to engage with the outer profile and the inner arm to axially interlock the outer profile with the inner arm, and wherein the locking handle is configured to move the locking structure from engagement with the outer profile and the inner arm to release the outer profile from axial interlocking with the inner arm when the outer profile is in the proximal position and the locking handle is moved from the distal pivot position towards the proximal pivot position.