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Joints alternate in their primary need — some want mobility (move freely), some want stability (resist unwanted motion) — and dysfunction at one tends to show up as pain or compensation at its neighbors.
Mobility is usable, controlled range of motion at a joint (see mobility-vs-flexibility). Stability is the ability to control or resist motion at a joint, keeping it well-positioned under load. Both are trainable qualities, and the goal of movement training is the right balance of each, joint by joint.
The joint-by-joint approach (popularized by Gray Cook and Mike Boyle) observes that joints alternate in their dominant requirement up the body:
| Joint / region | Primary need |
|---|---|
| Foot | Stability |
| Ankle | Mobility (esp. dorsiflexion) |
| Knee | Stability |
| Hip | Mobility |
| Lumbar spine | Stability |
| Thoracic spine | Mobility |
| Scapula / shoulder girdle | Stability |
| Glenohumeral (shoulder) | Mobility |
The clinical observation is that when a joint loses its primary quality, the adjacent joints compensate by taking on a role they are not built for — e.g., stiff ankles or hips push the lumbar spine (which wants stability) into excessive motion, a common contributor to low-back pain (see back-disorders-causes). Training therefore pairs mobility work at the mobility joints (ankle, hip, thoracic spine, shoulder; see dynamic-warmup-overview, exercise-90-90-hip-switch, exercise-ankle-mobility-drills) with stability work at the stability joints (lumbar/core, knee, scapula; see core-stability-vs-strength).
This is a heuristic, not an absolute rule — every joint needs some of both — but it is a useful lens for designing mobility-and-stability programs and interpreting compensations.
Educational content only — not medical advice. Always consult a qualified professional for individualized guidance, especially around injury, pregnancy, or medical conditions.