title: Diminished Foot and Ankle Muscle Volumes in Young Adults With Chronic Ankle Instability.
abstract: BACKGROUND
  Patients with chronic ankle instability (CAI) have demonstrated altered neuromuscular function and decreased muscle strength when compared with healthy counterparts without a history of ankle sprain. Up to this point, muscle volumes have not been analyzed in patients with CAI to determine whether deficits in muscle size are present following recurrent sprain.
  
  
  OBJECTIVE
  To analyze intrinsic and extrinsic foot and ankle muscle volumes and 4-way ankle strength in young adults with and without CAI.
  
  
  METHODS
  Cross-sectional study; Level of evidence, 3.
  
  
  METHODS
  Five patients with CAI (mean age, 23.0 ± 4 years; 1 male, 4 females) and 5 healthy controls (mean age, 23.8 ± 4.5 years; 1 male, 4 females) volunteered for this study. Novel fast-acquisition magnetic resonance imaging (MRI) was used to scan from above the femoral condyles through the foot and ankle. The perimeter of each muscle was outlined on each axial slice and then the 2-dimensional area was multiplied by the slice thickness (5 mm) to calculate the muscle volume. Plantar flexion, dorsiflexion, inversion, and eversion isometric strength were measured using a handheld dynamometer. Patients with CAI were compared with healthy controls on all measures of muscle volume and strength. Extrinsic muscle volumes of patients with CAI were also compared with a normative database of healthy controls (n = 24) by calculating z scores for each muscle individually for each CAI subject.
  
  
  RESULTS
  The CAI group had smaller total shank, superficial posterior compartment, soleus, adductor hallucis obliqus, and flexor hallucis brevis muscle volumes compared with healthy controls as indicated by group means and associated 90% CIs that did not overlap. Cohen d effect sizes for the significant group differences were all large and ranged from 1.46 to 3.52, with 90% CIs that did not cross zero. The CAI group had lower eversion, dorsiflexion, and 4-way composite ankle strength, all with group means and associated 90% CIs that did not overlap. No other significant differences were identified.
  
  
  CONCLUSIONS
  Patients with CAI demonstrate atrophy of intrinsic and extrinsic foot and ankle musculature accompanied by lower ankle strength.
  
  
  CONCLUSIONS
  Clinicians should be aware of the muscle atrophy and strength deficits when prescribing rehabilitation for patients with lateral ankle sprain or CAI.
authors: University of Virginia, Charlottesville, Virginia, USA.
authors: Mark A
authors: MA
authors: Feger
authors: University of Virginia, Charlottesville, Virginia, USA.
authors: Shannon
authors: S
authors: Snell
authors: University of Virginia, Charlottesville, Virginia, USA.
authors: Geoffrey G
authors: GG
authors: Handsfield
authors: University of Virginia, Charlottesville, Virginia, USA.
authors: Silvia S
authors: SS
authors: Blemker
authors: University of Virginia, Charlottesville, Virginia, USA.
authors: Emily
authors: E
authors: Wombacher
authors: University of Virginia, Charlottesville, Virginia, USA.
authors: Rachel
authors: R
authors: Fry
authors: University of Virginia, Charlottesville, Virginia, USA.
authors: Joseph M
authors: JM
authors: Hart
authors: University of Virginia, Charlottesville, Virginia, USA.
authors: Susan A
authors: SA
authors: Saliba
authors: University of Virginia, Charlottesville, Virginia, USA.
authors: Joseph S
authors: JS
authors: Park
authors: University of Virginia, Charlottesville, Virginia, USA.
authors: Jay
authors: J
authors: Hertel
keywords: ankle sprain; intrinsic foot muscles; muscle morphology; strength