A patient stands facing the wall and performs a wall push-up during assessment. The therapist observes the medial border of the patient's left scapula lift off the thorax. Which is indicated in the assessment?

When assessing scapular stability and movement, the observation of the medial border of the scapula (specifically the left scapula in this case) lifting off the thorax during a wall push-up indicates a weakness of the serratus anterior muscle.

The serratus anterior plays a crucial role in stabilizing the scapula against the ribcage while allowing for proper shoulder mechanics. During push-up movements, the serratus anterior contracts to hold the scapula in place, thus preventing it from winging. If there is weakness in this muscle, it can result in the scapula lifting away from the thoracic wall, demonstrating reduced control and stability. This condition is often referred to as "scapular winging."

Understanding the roles of various muscles in shoulder stability is essential for clinicians to assess and create effective rehabilitation programs. In this scenario, it is the weakness of the serratus anterior that directly leads to the observed dysfunction during the patient's wall push-up. Strengthening exercises targeting the serratus anterior would typically be indicated as part of the treatment plan following such a finding.