What clinical presentation is caused by an unilateral contracture of the sternocleidomastoid?

The clinical presentation resulting from a unilateral contracture of the sternocleidomastoid muscle leads to lateral head flexion toward the side of the contracture with corresponding contralateral rotation of the head. This characteristic is due to the specific muscle actions of the sternocleidomastoid; when one side is contracted, it creates a torque that tilts the head toward that side while simultaneously rotating the face to the opposite side.

In this situation, the shortened muscle on one side pulls the head into a position that characterizes a specific asymmetrical posture, known in clinical terms as torticollis or wry neck. The relationship between the contractions of the muscles dictates this movement pattern. Understanding the mechanics of the sternocleidomastoid is essential for recognizing how this contraction can influence head and neck positioning in an individual with such a condition.

Other options do not accurately reflect the clinical presentation produced by this unilateral muscle contracture. For example, a forward head position may develop as a secondary posture due to other muscular imbalances or conditions but is not the immediate presentation of a unilateral sternocleidomastoid contracture. Neck extension with shoulder elevation does not represent a typical contracture effect of this muscle alone and would involve additional muscular activity