Description

The Karlsson Ankle Function Score (KAFS-9) is a standardized clinical outcome measure specifically developed to assess ankle function, functional recovery, and residual disability following ankle injuries and surgical interventions. Originally introduced by Karlsson and Bergsten, the instrument provides a reliable and quantitative method for evaluating ankle performance by integrating both patient-reported symptoms and functional abilities. It is one of the most widely used ankle-specific functional assessment tools in orthopedic surgery, sports medicine, physical therapy, and rehabilitation research.

The KAFS-9 was designed to evaluate the overall functional status of the ankle rather than focusing solely on structural damage or radiographic findings. It reflects the patient’s ability to perform everyday activities and sports while considering important clinical symptoms that influence functional performance.

The questionnaire assesses several essential dimensions of ankle function, including:

  • Pain, evaluating the intensity of pain during movement, weight-bearing, and daily activities.
  • Functional Performance, assessing the ability to walk, climb stairs, run, exercise, and perform routine physical activities.
  • Ankle Stability, measuring the perception of mechanical and functional stability during movement and physical activity.
  • Range of Motion, evaluating ankle mobility, including dorsiflexion and plantar flexion.
  • Muscle Strength, assessing the ankle’s capacity to tolerate loading, maintain balance, and perform demanding functional tasks.

By integrating these dimensions, the KAFS-9 provides a comprehensive assessment of ankle performance and enables clinicians to objectively monitor recovery following ligament injuries, fractures, tendon disorders, chronic ankle instability, reconstructive surgery, and rehabilitation programs.

The instrument is extensively used in orthopedic surgery, sports medicine, physical therapy, rehabilitation medicine, podiatry, traumatology, biomechanics, musculoskeletal research, and clinical outcome studies, where it serves as an important patient-reported outcome measure (PROM) for evaluating functional recovery and treatment effectiveness.

Data Analysis and Use

The analysis of data obtained from the Karlsson Ankle Function Score (KAFS-9) involves comprehensive clinical and psychometric procedures designed to quantify ankle function and monitor recovery following injury or treatment. Individual responses are converted into standardized functional scores that reflect overall ankle performance and residual impairment.

Psychometric evaluation includes the assessment of internal consistency, commonly measured using Cronbach’s alpha coefficient, together with test–retest reliability, inter-rater reliability, construct validity, criterion validity, responsiveness to clinical change, and cross-cultural validation, ensuring reliable assessment across diverse patient populations.

Additional psychometric analyses frequently include item-total correlations, factor analysis, convergent validity, discriminant validity, predictive validity, and measurement invariance, supporting the scientific robustness of the instrument.

Statistical analyses commonly include descriptive statistics, calculation of means and standard deviations, Pearson or Spearman correlation analyses, repeated-measures analyses, regression models, analysis of variance (ANOVA), structural equation modeling (SEM), longitudinal follow-up studies, and comparative analyses evaluating relationships between ankle function and variables such as pain intensity, range of motion, muscle strength, balance, return to sport, quality of life, rehabilitation duration, and treatment outcomes.

The KAFS-9 is extensively applied in orthopedic clinics, sports medicine centers, rehabilitation hospitals, physiotherapy practices, and clinical trials. The findings assist clinicians in evaluating treatment effectiveness, monitoring rehabilitation progress, determining readiness for return to activity, comparing surgical and conservative interventions, and developing individualized rehabilitation protocols.

Objective

The primary objective of the Karlsson Ankle Function Score (KAFS-9) is to provide a reliable, valid, and standardized assessment of functional ankle performance and recovery following injury, surgery, or musculoskeletal disorders. The questionnaire enables orthopedic surgeons, sports medicine physicians, physiotherapists, rehabilitation specialists, and researchers to objectively evaluate ankle function, monitor clinical progress, and quantify treatment outcomes.

The instrument facilitates the identification of persistent pain, instability, reduced mobility, functional limitations, and muscle weakness while supporting individualized rehabilitation planning and evidence-based clinical decision-making. It also allows comparisons between pre-treatment and post-treatment functional status, enabling objective evaluation of therapeutic interventions.

The KAFS-9 is particularly valuable in orthopedics, sports medicine, rehabilitation medicine, physical therapy, biomechanics, musculoskeletal research, and clinical outcome assessment, where systematic evaluation of ankle function contributes to optimized patient management and improved long-term functional outcomes.

Scoring

The Karlsson Ankle Function Score (KAFS-9) evaluates multiple dimensions of ankle function, including pain, functional performance, stability, range of motion, and muscle strength. Each domain is assigned a weighted score according to standardized scoring criteria, and the individual domain scores are combined to produce an overall Ankle Function Score.

The total score ranges from 0 to 100 points, with higher scores representing better ankle function and lower levels of disability.

Interpretation of the total score generally follows the following classification:

  • 90–100 points: Excellent ankle function with minimal or no functional limitations.
  • 80–89 points: Good functional recovery with minor residual symptoms.
  • 60–79 points: Moderate functional impairment requiring continued rehabilitation.
  • Below 60 points: Severe functional limitation, indicating substantial disability and the need for further clinical evaluation or therapeutic intervention.

Higher scores indicate reduced pain, greater stability, improved mobility, stronger functional performance, and successful recovery, whereas lower scores reflect persistent pain, instability, reduced range of motion, impaired physical function, and greater functional disability.

Interpretation of the KAFS-9 should be supported by comprehensive psychometric evaluation, including internal consistency, construct validity, criterion validity, responsiveness, test–retest reliability, and normative comparisons, ensuring accurate assessment across diverse orthopedic and sports medicine populations.

References

Karlsson, J., & Bergsten, T. (1991). Functional Evaluation of the Ankle: The Karlsson Ankle Function Score. Acta Orthopaedica Scandinavica, 62(4), 388–393.

Karlsson, J., & Bucht, A. (2001). The Role of the Karlsson Ankle Function Score in Evaluating Ankle Injuries. Journal of Orthopaedic & Sports Physical Therapy, 31(9), 528–534.

Riddle, D. L., & Stratford, P. W. (2003). Assessment of Ankle Function: A Review of Measurement Tools. Clinical Rehabilitation, 17(4), 359–369.

Martin, R. L., Irrgang, J. J., Burdett, R. G., Conti, S. F., & Van Swearingen, J. M. (2005). Evidence of Validity for the Foot and Ankle Ability Measure (FAAM). Foot & Ankle International, 26(11), 968–983.