# Lower Limb Joint Coordination and Coordination Variability During Landing: A Scoping Review
## 3 Results
### Injured or At-Risk Individuals  
Several studies have examined lower limb coordination during landing in individuals with a history of injury or those considered at elevated risk. A common theme across these populations is disrupted joint synergy, often reflected as either rigid, low-variability strategies or excessive, erratic variability, depending on the injury type. **ACL Reconstruction (ACLR):** Following ACL injury and reconstruction, individuals often display persistent alterations in joint coordination. [PERSON], [PERSON] [14], and [PERSON] [29] observed that ACLR patients commonly adopt a rigid coordination strategy with reduced variability, particularly in hip-knee couplings. These patterns, often interpreted as protective or compensatory, suggest constrained joint motion and reduced neuromuscular flexibility. Frontal-plane coordination, for instance, may shift toward greater hip control to compensate for knee instability [30]. These deficits can persist well beyond clinical recovery, underscoring the limitations of standard rehabilitation in fully restoring dynamic inter-joint control. **Chronic Ankle Instability (CAI):** Individuals with chronic ankle instability, typically due to recurrent lateral ankle sprains, also display unique coordination adaptations [7; 31]. In contrast to ACLR, where reduced variability is common, CAI individuals have been reported to show _increased_ joint coupling variability during landing [32]. [PERSON], [PERSON] [16] examined drop vertical jumps in a cohort with chronic ankle instability and found significantly higher variability in lower extremity joint coupling compared to healthy controls. In that study, trial-to-trial coordination variability was elevated particularly in couplings involving the injured ankle, suggesting inconsistency in how the ankle and more proximal joints work together on each landing. The authors interpreted higher coupling variability as a possible sensorimotor deficit (the unstable ankle may lead to erratic motor patterns as the body struggles to stabilize, resulting in less repeatable coordination). Interestingly, this finding is the opposite of what is often seen in high-risk ACL mechanisms; instead of being too rigid, CAI landing patterns might be too variable or poorly controlled. Coordination and symmetry analyses have also revealed that individuals with CAI can exhibit altered \begin{table}
\begin{tabular}{c c} \hline \hline
**Term** & **Definition** \\ \hline In-phase & \begin{tabular}{c} Joints move in the same direction and at similar \\ timing during a task (i.e., simultaneous hip and \\ knee flexion). \\ \end{tabular} \\ \hline Anti-phase & \begin{tabular}{c} Joints move in opposite directions or out of sync \\ (i.e., hip flexion paired with knee extension). \\ \end{tabular} \\ \hline Proximal dominance & \begin{tabular}{c} Greater movement or control observed at the \\ more proximal joint (i.e., hip over knee). \\ \end{tabular} \\ \hline Distal dominance & \
\begin{tabular}{c} Greater movement or control observed at the \\ more distal joint (i.e., ankle over knee). \\ \end{tabular} \\ \hline Coordination variability &
\begin{tabular}{c} The trial-to-trial variation in joint coupling or \\ movement strategy, indicating movement \\ consistency or adaptability. \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Key coordination terminology for coordination analysis and interpretation. inter-limb coordination [33]. As an example, comparisons of drop jump landings between the injured ankle side and the uninjured (or between the CAI group and \"copers\" who had ankle grains but no instability) indicate that CAI is associated with asymmetric coordination patterns (the unstable limb may not mirror the movement strategy of the other limb) [34; 35]. **Other At-Risk Populations:** Some studies have looked at coordination in individuals predisposed to injury even if they have no current injury.