Detect stiff-knee gait (reduced / delayed peak swing knee flexion)

Stiff-knee gait is marked by reduced peak knee flexion in swing (normal \(\approx 60^{\circ}\) near 73\ (Perry & Burnfield; Goldberg et al. 2006).

Usage

detectStiffKnee(
  knee_flexion,
  swing = c(60, 100),
  normal_peak = 60,
  threshold = 45,
  severe_floor = 10,
  delay_threshold = 80
)

Arguments

knee_flexion: Knee flexion angle (degrees, flexion positive) over one normalised gait cycle.
swing: Percentage window of swing phase (default c(60, 100)).
normal_peak: Normal peak swing knee flexion in degrees (default 60).
threshold: Peak below which stiff-knee is flagged (default 45).
severe_floor: Peak flexion mapped to severity 1 (default 10).
delay_threshold: Peak-timing percentage above which the peak is considered delayed (default 80).

Value

A gait_pattern_flag object.

References

Perry J, Burnfield JM (2010); Goldberg SR, et al. (2006).

Examples

# normal knee flexion peaks ~60 deg in swing
k <- c(seq(5, 18, length.out = 30), seq(18, 5, length.out = 30),
       60 * sin(seq(0, pi, length.out = 41)))
detectStiffKnee(k)
#> <gait_pattern_flag> stiff_knee: normal (severity 0.00)
#>   peak_swing_knee_flexion_deg = 60 (threshold 45, normal 60)