The factor which does not contribute to the strength and stability of a synovial joint is the Synovial Fluid

Explanation:
Firstly, what are synovial joints? Synovial joints basically are the joints that can move in many directions.

Examples of these joints are hips, shoulders, elbow, knees, wrists and ankles.

These are filled with synovial fluid which is a lubricant for the joints so that they can move easily but it doesn’t strengthen or stabilises the joint. Rather it just helps in smooth functioning.