Slocum's Test


The Slocum’s test (1976) represents a modification of the Anterior Drawer test [1] which tests anteromedial rotary instability (AMRI) and anterolateral rotary instability (ALRI) of the knee. [2]
The anterior drawer test evaluates the anterior cruciate ligament. When inserting an internal or external rotation to this test, anterolateral and anteromedial rotary instability can be evaluated.

Clinically Relevant Anatomy

Following structures may be involved when the test comes out positive:
-Anterolateral: Anterior and posterior cruciate ligament, posterolateral capsule, arcuate – popliteus complex, lateral collateral ligament and iliotibial band.
-Anteromedial: Anterior cruciate ligament, medial collateral ligament, posterior oblique ligament, posteromedial capsule. [3]


Testing for anterior rotatory instability of the knee.


The patient is lying supine with the knee flexed 90 degrees and the foot fixed to the examining table by the examiner. 30 degrees of internal rotation is applied to the tibia by rotating the foot. The examiner pulls anteriorly on the tibia to assess for anterolateral rotary instability. Results are compared bilaterally.
Positive: Increased amount of anterior tibial translation with tibial internal rotation or
excessive movement on the lateral aspect of the knee indicates anterolateral instability. [3]
Anterolateral rotatory instability (ALRI) is a manifestation of an anterior cruciate ligament (ACL) deficient knee. [4]
This technique allows the hamstrings to relax because of the 90 degrees flexion of the knee (origin and insertion of the hamstrings are closer to each other in flexion). [5]

To examine anteromedial rotary instability the tibia is laterally rotated 15 degrees and the tibia is once again pulled forward. Results are compared bilaterally.
Positive: When pathologically increased forward and outward displacement of the tibia on the femur is possible, [3]excessive anterior rotation of the medial tibial plateau indicates laxity of the medial structures. [4]

There’s also another technique described for the anterolateral rotatory instability test
The patient is lying on his or her uninvolved side and uninvolved hip and knee flexed. The patient rolls the pelvis backward until it reaches a position that is 30 degrees from the supine position. The medial side of the foot of the involved extremity is placed firmly on the surface of the examining table with the knee in full extension. This position eliminates any rotation of the hip, allows the knee to fall into a valgus position and causes internal rotation of the tibia on the femur.
With both hands placed on the lateral aspect of the knee joint, while the patient slowly flexes the knee, the examiner assists this maneuver and also exerts downward pressure to produce a valgus stress on the knee and anterior subluxation of the tibia if rotatory instability is present. The subluxation can be seen and felt to reduce as the knee flexes from 25 to 40 degrees of flexion.[6]

last checked: 2011.01.03



  1. Postsurgical orthopedic sports rehabilitation: knee and shoulder – Robert C Manske
  2. Kaplan National Physical Therapy exam – Bethany Chapman, Mary Friatinni
  3. 3.0 3.1 3.2 Neuromusculoskeletal examination and assessment: a handbook for therapists – Nicola F Petty, Ann P Moore
  4. 4.0 4.1 Larson RL, Physical examination in the diagnosis of rotatory instability, clin orthop relat res, 1983, 172, 38-44
  5. Donald B. Slocum, Robert L Larson. Rotatory Intability of the Knee: its pathogenesis and a clinical test to demonstrate its presence. The journal of Bone and Joint Surgery, american volume, 1968; 50-A, No.2:211-225.
  6. J C Kennedy, F.R.C.S, Roger Stewart and Dennis M. Walker. Anterolateral rotatory instability of the knee joint: an early analysis of the elisson procedure, The journal of bone and joint surgery. 1978; Vol 60-A, No 8; 1031-1039.