The study is a quality assurance study, aiming to determine the agreement between two different measurement instruments for assessing knee joint laxity in patients with ACL injuries.

The study aims to include 60 patients with previous ACL injury, recruited in an outpatient clinic at Aarhus University Hospital from September 2022 to March 2023. For patients who consent to participate in the study, their knee joint laxity in both the injured and the non-injured knee is assessed using both a Rolimeter and a Lachmeter. Subsequently, the collected data are examined to determined the agreement between the two measurement instruments.

Methods:

In connection with their visit at either the orthopaedic or physiotherapy outpatient clinic, patients are invited to participate in the study. Patients consenting to participate will undergo knee joint laxity tests with both the Rolimeter and the Lachmeter, and in addition health-related and demographic data are collected.

The two tests are performed in random order for each patient, and the same physiotherapist conducts the two tests in each individual patient. The physiotherapist performing the two tests reads and notes the score on the first test, while a different physiotherapist, blinded to the score of the first test, reads and notes the score on the second test.

Agreement between the two scores are investigated using a Bland-Altman plot, with calculation of bias and upper and lower limits of agreements with 95% CIs. A priori, an acceptable difference between the two methods is set at 1 millimeter.

Inclusion Criteria:

• Patients with ACL injury awaiting potential ACL-surgery
• Patients with previous ACL-surgery

Exclusion Criteria:

• Multiligament injury
• PCL injury

Patients are recruited consecutively from either the orthopaedic outpatient clinic (patients with ACL-injury) or the physiotherapy outpatient clinic (patients who have previously undergone ACL surgery) at Aarhus University Hospital.