Serratus Anterior

Clinical Notes

• The long thoracic nerve (C5–C7) has an unusually long and superficial course — it runs down the lateral thoracic wall on the surface of the serratus anterior. This superficial course makes it vulnerable to compression, traction, and surgical injury. Long thoracic nerve palsy produces serratus anterior paralysis and dramatic scapular winging.

• One of the "weak" muscles in conditions/upper-crossed-syndrome. Serratus anterior is reciprocally inhibited by shortened pectoralis minor. When serratus is inhibited, the scapula loses its ability to upwardly rotate and posteriorly tilt, contributing to conditions/subacromial-impingement.
• Part of the scapular upward rotation force couple with upper trapezius and lower trapezius. Weakness of any member of this force couple disrupts shoulder mechanics above 90° of elevation.
• Long thoracic nerve palsy — produces medial scapular winging (the medial border lifts off the rib cage). This can result from surgical injury, viral neuritis (Parsonage-Turner syndrome), or traction injury from carrying heavy loads on the shoulder.
• Serratus anterior weakness contributes to conditions/thoracic-outlet-syndrome — without adequate protraction, the scapula sits retracted and depressed, narrowing the costoclavicular space.

• In clients with upper crossed syndrome, serratus anterior is inhibited and weak bilaterally. The scapulae are protracted (by pectoralis minor) but without the stabilizing upward rotation and posterior tilt that serratus provides. This paradox is important: the scapula is protracted but the wrong muscles are doing the protracting.
• The wall push-up test is the fastest screen — have the client do a wall push-up and observe from behind. If the medial scapular border lifts off the rib cage, serratus anterior is weak.
• Serratus anterior TrPs on the lateral rib cage are often surprisingly tender. Clients may report a "side stitch" sensation during palpation.

• TrPs respond to sustained compression over the lateral rib cage. Use broad fingertip pressure — the ribs are directly underneath. Hold for 30–60 seconds per TrP.
• The clinical priority for serratus anterior is activation, not release. Serratus anterior punches (supine scapular protraction against resistance), wall slides with scapular protraction, and dynamic hugs are more valuable than manual therapy alone.
• Post-treatment and strengthening, scapular winging should reduce and overhead shoulder mechanics should improve.

• The ribs are directly beneath the serratus anterior — use broad pressure, not focused tool pressure. In clients with osteoporosis, use minimal force.
• The long thoracic nerve runs superficially on the muscle — avoid sustained deep pressure along the mid-axillary line, particularly in the upper thoracic region.
• The lateral thoracic artery runs along the lower border of the pectoralis minor, superficial to the serratus anterior. Avoid deep pressure in this area.
• This area can be ticklish — communicate before palpating the lateral rib cage.

• Serratus anterior is the key muscle for scapular posterior tilt during overhead elevation. When it is weak, the scapula anteriorly tilts (driven by the shortened pectoralis minor), narrowing the subacromial space. Strengthening serratus anterior is the single most important exercise intervention for scapular-driven shoulder impingement.

• Scapular protraction can be produced by either serratus anterior or pectoralis minor — but the scapular position is different. Serratus anterior protracts with posterior tilt and upward rotation (healthy scapular position). Pectoralis minor protracts with anterior tilt and downward rotation (pathological scapular position). If the client's scapulae are protracted AND anteriorly tilted, the protraction is being driven by pectoralis minor, and serratus anterior is inhibited. The treatment is to release pectoralis minor and strengthen serratus anterior.