The Controversial Anterolateral Knee Complex - Part 1

The most common ligamentous injury in the knee - an anterior cruciate ligament (ACL) tear - is getting a sideways glance from researchers. What set off this scrutiny is the ‘failure’ rate of ACL reconstruction, with 25% of post procedure knees demonstrating rotational instability, up to 25% of young athletes suffering a second ACL injury, and just 55% of athletes returning to a competitive level of play ^(1,2).This frustration has led researchers to re-examine the anterolateral knee complex and the role of other structures in lateral and rotational stability.

What’s old is new again

In 2013, researchers in Belgium examined the anterolateral knee complex in 41 embalmed cadaveric knees⁽³⁾. They identified the presence of a ‘new’ ligament they called the alterolateral ligament (ALL) in all but one specimen. They hypothesised that this ligament helped control internal tibial rotation and contributed to knee stability. Perhaps this was the missing link that explained why knees post ACL repair still demonstrated pivot shift laxity? (see Figures 1a-c) This set off a firestorm of research to both validate and refute the very existence of the ALL and its role in knee stability.

The existence of the ALL is actually not a ‘new’ phenomenon, but rather a rediscovery. French surgeon Paul Segond first identified the ALL in 1879 when he described a fracture of a small piece of bone from the lateral rim of the proximal tibia. He noted that the bone was avulsed by a shiny fibrous band on the anterolateral capsule of the knee. From that time, this lateral thickening was called by several different names in the medical literature, such as the anterior band of the lateral collateral ligament, lateral capsular ligament, or anterior oblique band.

In the 1970s, researchers correlated a ‘Segond fracture’ (easily visible on X-ray), with an ACL injury. Despite this resurgence of recognition, the role of the ALL in ACL injury and knee stability was overshadowed by the advent of knee arthroscopy in the later half of that decade. Even with the high success rate of technically correct arthroscopic procedures to repair the ACL (75% to 97%), knee instability remained a problem.

Tests for ACL integrity

*Note that clinicians should perform tests on both sides and record differences between the movement of the injured side versus the uninjured side.

Pivot shift test⁽⁴⁾ (Figure 1a below)

1. Note that the patient’s knee is fully extended. Internally rotate the leg and apply a valgus stress.
2. As the clinician flexes the knee between 20 and 45 degrees, the lateral tibial plateau is subluxed.
3. As tension in the iliotibial band is lessened at 45 degrees of flexion, a pivot shift is felt as the tibia is reduced. This test identifies a rupture of the anterior cruciate ligament. Note that some knees demonstrate a positive pivot shift, even with a surgically corrected ACL⁽⁴⁾.