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Test: Seated Tibial Rotation - Passive
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Background/Purpose
The knee is usually described as a hinge, but it's more accurately a modified hinge. Alongside flexion and extension, the tibia can rotate on the femur around its long axis, and that rotation matters for normal mechanics, joint stability, and many of the injuries you see in practice.
How much rotation, and when
Tibial rotation depends on the knee's flexion angle. In full extension there is almost none: the femoral condyles sit congruently on the tibial plateau and the cruciates, collaterals, and posterior capsule are taut, so the joint is locked. As the knee flexes, the ligaments slacken and the joint surfaces become less congruent, so rotation increases. It peaks around 90° of flexion, where most sources put total rotation at roughly 40–50°. External rotation is usually somewhat greater than internal, about 30–40° versus 20–30°, though reported values vary with method and population. This is why rotational tests are done in flexion, and why the dial test uses both 30° and 90°: different structures dominate the restraint at each angle.
The screw-home mechanism
In the last 20–30° of extension, the tibia externally rotates about 5–10° on the femur (open chain), or the femur internally rotates on the tibia (closed chain). Three factors drive this: the medial femoral condyle's articular surface is longer than the lateral one, the ACL tightens, and the quadriceps pulls laterally. Together they lock the knee into a stable, low-energy position for standing. Unlocking is mainly the popliteus's job: it internally rotates the tibia (or externally rotates the femur) to start flexion from full extension. A knee that can't complete screw-home, because of effusion, a meniscal block, osteoarthritis, or a flexion contracture, loses that passive stability and depends more on muscle for standing control.
What restrains rotation
External tibial rotation is resisted mainly by the posterolateral corner (the LCL, popliteus tendon, and popliteofibular ligament), with the superficial MCL contributing and the PCL becoming more important at higher flexion angles. Internal rotation is resisted by the ACL, the anterolateral capsule and anterolateral ligament, and the iliotibial band. The dynamic restraints are the medial hamstrings, sartorius, gracilis, and popliteus as internal rotators, and the biceps femoris as the main external rotator. Because the static and dynamic systems overlap, a patient with a ligament injury can sometimes compensate muscularly, and rotational laxity is easier to detect when the patient is relaxed.
Clinical relevance
Ligamentous instability. Excess rotation usually shows up as rotatory instability rather than straight-plane laxity. Anterolateral rotatory instability (ACL with anterolateral structures) is what the pivot shift detects. Posterolateral rotatory instability (PLC, with or without the PCL) is what the dial test detects. Missing a posterolateral corner injury is a well-recognized cause of ACL reconstruction failure, which is why rotational testing belongs in any workup of a significant knee injury.
Meniscal pathology. The menisci move with tibial rotation, and rotation under compressive load creates shear across them, especially the posterior horns. Most meniscal provocation tests use this mechanism: McMurray, Apley compression, and Thessaly. The medial meniscus is less mobile than the lateral because of its capsular and MCL attachments, which is one reason it's injured more often.
Injury mechanism. Non-contact ACL injuries typically involve valgus collapse combined with tibial rotation on a planted foot, often during deceleration or cutting. Assessing and training rotational control, including hip and trunk control of femoral position, is central to prevention and return-to-sport programs.
Kinetic chain effects. Subtalar pronation is coupled with tibial internal rotation, and supination with external rotation. Excessive or poorly timed pronation can change rotational demands at the knee and has been linked to patellofemoral and medial knee complaints. Femoral internal rotation from weak hip abductors and external rotators produces a similar relative rotation at the knee from above. This is a common reason knee complaints respond to treatment at the hip or foot.
Patellofemoral function. Relative tibial external rotation moves the tibial tuberosity laterally and increases the lateral pull on the patella, which is relevant in patellofemoral pain and patellar maltracking.
Osteoarthritis. Degenerative knees often show altered rotational kinematics, including a reduced screw-home mechanism and changed tibiofemoral contact patterns. These can concentrate load in the medial compartment and may contribute to disease progression.
Procedure
Patient sits on the edge of the table with the lower leg off the table and knee flexed and clinician passively internally and externally rotates the tibia.
Performed: Unilaterally
Dialog
Patient sits on the edge of the table with the lower leg off the table and knee flexed and clinician passively internally rotates the tibia.Criteria
- 20 degrees internal rotation
- 40 degrees external rotation
Measurement
20-40 degreesLOINC Code
Scale/Grading
selection range; grade - LOINC IDTest Stats
-
Side Pass Fail Left 0 0 Right 0 0 Avg. Measure. Left 0.0 0.0 Avg. Measure. - Right 0.0 0.0