An abnormal increase in hyperextension usually indicates damage to not only the posterolateral structures but the ACL as well.
The triple varus knee, described in detail in Chapter 31, Primary, Double, and Triple Varus Knee Syndromes: Diagnosis, Osteotomy Techniques, and Clinical Outcomes, refers to varus alignment caused by three factors: tibiofemoral varus osseous malalignment, increased lateral tibiofemoral compartment separation due to marked insufficiency of the FCL and PMTL, and varus recurvatum in extension. The varus recurvatum position of the knee will be markedly worse if there is associated osseous tibiofemoral varus malalignment.
An abnormal knee hyperextension gait pattern involves increased extension (>0°) in the sagittal plane and, frequently, associated varus malalignment in the coronal plane (varus recurvatum). The gait abnormality described in this chapter is easily identifiable in the clinic if the examiner devotes a small amount of time to observation during the initial patient presentation. The comprehensive physical examination and radiographic evaluation required to determine all of the abnormalities that exist in these complex knee joint injuries are detailed in Chapter 21, Posterior Cruciate Ligament: Diagnosis, Operative Techniques, and Clinical Outcomes, and 31, Primary, Double, and Triple Varus Knee Syndromes: Diagnosis, Osteotomy Techniques, and Clinical Outcomes.įIGURE 34-1 A lower limb varus deformity and hyperextension gait abnormality are evident in this 32-year-old man with chronic deficiency of the posterolateral structures and varus malalignment. 5, 7, 11 In addition, many knees with insufficiency to the posterolateral structures also have varus osseous malalignment. 8, 9, 12, 13, 19, 26 Posterolateral injuries are frequently accompanied by a rupture to the anterior cruciate ligament (ACL) and, in some cases, a rupture to the posterior cruciate ligament (PCL). These structures function together to resist lateral tibiofemoral compartment opening, posterior subluxation of the lateral tibial plateau with tibial rotation, knee hyperextension, and varus recurvatum (see Chapter 20, Function of the Posterior Cruciate Ligament and Posterolateral Ligament Structures). The primary lateral and posterolateral structures of the knee joint are the fibular collateral ligament (FCL) and popliteus muscle-tendon-ligament unit (PMTL), including the popliteofibular ligament (PFL) and the posterolateral capsule (PLC). It is well appreciated that patients with chronic insufficiency of the lateral and posterolateral structures of the knee may develop a gait abnormality characterized by excessive knee hyperextension during the stance phase (initial contact or heel-strike, loading response, midstance, and toe-off) of the gait cycle ( Fig.
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