Known-group validity of passive knee joint position sense: a comparison between individuals with unilateral anterior cruciate ligament reconstruction and healthy controls.

BACKGROUND: Knee joint position sense (JPS) might be negatively affected after injuries to the anterior cruciate ligament (ACL). Recent systematic reviews suggest further investigation of psychometric properties, including validity, of knee JPS tests following ACL reconstruction (ACLR). This study investigated the known-group validity by comparing knee JPS errors between individuals who underwent unilateral ACLR and healthy controls. METHODS: This cross-sectional study involved 36 men, including 19 after ACLR (ACLR group) and 17 healthy controls (control group). In both groups, the absolute error (AE), constant error (CE) and variable error (VE) of passive knee JPS were calculated in the flexion and extension directions, for two target angles (30° and 60° flexion) per direction. Discriminative validity was evaluated by comparing JPS errors between the operated and non-operated knees in the ACLR group. Known-group validity was evaluated by comparing JPS errors between the operated knees in the ACLR group and the asymptomatic non-dominant knees of healthy controls. RESULTS: Mean AE, CE and VE for all tests were 4.1°, - 2.3° and 3.6° for the operated knees in the ACLR group, 5.5°, - 2.6° and 3.3° for the non-operated knees in the ACLR group and 4.6°, - 2.6° and 3.3° for the non-dominant knees in the control group, respectively, regardless of the test direction and target angle. The operated knees in the ACLR group did not show significantly greater JPS errors compared to the contralateral knees in the ACLR group and to the non-dominant knees in the control group (p ≥ 0.05). On the other hand, the non-operated knees showed significantly greater AE for the 0°-60° flexion test (p = 0.025) and CE for the 0°-30° flexion test (p = 0.024) than the operated knees in the ACLR group. JPS errors did not significantly differ in the operated knees in the ACLR group based on the direction of movement and the target angle. However, the errors were significantly higher when the knee was moved through a greater range compared to that of a lesser range between the starting and target angles. CONCLUSION: The ACLR knees did not show greater passive JPS errors than the contralateral or control knees. The direction of movement and target angle did not influence the JPS acuity after ACLR. However, higher JPS errors were evident when the knee was moved through a greater range compared to a lesser range of motion. Further studies investigating the psychometric properties of standardized JPS tests following ACLR are warranted.

Test-Retest Reliability of a Passive Joint Position Sense Test After ACL Reconstruction: Influence of Direction, Target Angle, Limb, and Outcome Measures.

Background: The joint position sense (JPS) is an element of proprioception and defined as an individual's ability to recognize joint position in space. The JPS is assessed by measuring the acuity of reproducing a predetermined target angle. The quality of psychometric properties of knee JPS tests after anterior cruciate ligament reconstruction (ACLR) is uncertain. Purpose/Hypothesis: The purpose of this study was to evaluate the test-retest reliability of a passive knee JPS test in patients who underwent ACLR. We hypothesized that the passive JPS test would produce reliable absolute error, constant error, and variable error estimates after ACLR. Study Design: Descriptive laboratory study. Methods: Nineteen male participants (mean age, 26.3 ± 4.4 years) who had undergone unilateral ACLR within the previous 12 months completed 2 sessions of bilateral passive knee JPS evaluation. JPS testing was conducted in both the flexion (starting angle, 0°) and the extension (starting angle, 90°) directions in the sitting position. The absolute error, constant error, and variable error of the JPS test in both directions were calculated at 2 target angles (30° and 60° of flexion) by using the angle reproduction method for the ipsilateral knee. The standard error of measurement (SEM), smallest real difference (SRD), and intraclass correlation coefficients (ICCs) with 95% Cis were calculated. Results: ICCs were higher for the JPS constant error (operated and nonoperated knee, 0.43-0.86 and 0.32-0.91, respectively) compared with the absolute error (0.18-0.59 and 0.09-0.86, respectively) and the variable error (0.07-0.63 and 0.09-0.73, respectively). The constant error of the 90°-60° extension test showed moderate to excellent reliability for the operated knee (ICC, 0.86 [95% CI, 0.64-0.94]; SEM, 1.63°; SRD, 4.53°), and good to excellent reliability for the nonoperated knee (ICC, 0.91 [95% CI, 0.76-0.96]; SEM, 1.53°; SRD, 4.24°). Conclusion: The test-retest reliability of the passive knee JPS tests after ACLR varied depending on the test angle, direction, and outcome measure (absolute error, constant error, or variable error). The constant error appeared to be a more reliable outcome measure than the absolute error and the variable error, mainly during the 90°-60° extension test. Clinical Relevance: As constant errors have been found reliable during the 90°-60° extension test, investigating these errors-in addition to absolute and variable errors-to reflect bias in passive JPS scores after ACLR is warranted.