The majority of<unk>  knee<unk>  occur in combination with another ligamentous injury, such as a cruciate ligament tear. This can make the diagnosis difficult and calls for the use of plain film radiographs and MRI to aid in the diagnosis. During the physical exam, it is imperative to assess a patient for signs of nerve injury as up to 15% of PLC<unk>  have associated nerve damage. Numbness, tingling, and/or dorsiflexor/great toe extensor muscle weakness all may suggest possible nerve damage. Radiographs Normal antero-posterior (AP) radiographs are useful to look for Segond fractures and fibular head avulsion fractures. Bilateral varus stress AP radiographs comparing the injured leg to the normal side are useful in assessing the lateral joint space for opening after a potential injury. More than a 2.7 mm increase between sides indicates a fibular collateral ligament tear, while greater than 4.0 mm indicates with a grade III<unk>  knee injury. Posterior stress radiographs taken with the patient kneeling show the amount of posterior tibial translation in both knees and are helpful to diagnose PCL insufficiency and combined<unk> . Between 0–2 mm increased posterior translation between the affected and healthy knees is normal, 2–7 mm indicates a partial tear, 8–11 mm suggests a complete tear and greater than 12 mm suggests a combined PCL and PLC injury. MRI High quality MRI images (1.5 T magnet or higher ) of the knee can be extremely useful to diagnose<unk>  to the<unk><unk>  and other major structures of the knee. While the standard coronal, sagittal and axial films are useful, thin slice (2 mm ) coronal oblique images should also be obtained when looking for PLC<unk> . Coronal oblique images should include the fibular head and styloid to allow for evaluation of the FCL and popliteus tendon. Specialized tests In addition to a complete physical examination of the lower extremity, there are a set of specialized tests that must be synthesized to specifically check for<unk>  to the<unk><unk> . It is always important when evaluating an extremity for injury to compare it with the normal side to make sure you are not seeing a normal variation within that patient: *External Rotation Recurvatum Test - One of the first tests developed to assess the PLC, the external rotation recurvatum test is performed with the patient lying supine. The practitioner stabilizes the distal thigh with one hand while lifting the great toe with the other. The injured side is compared to the healthy one and a positive test is indicated by an increased amount of recurvatum, or hyperextension, in the affected knee. Increased recurvatum indicates possible combined<unk>  to the<unk><unk>  and cruciate ligaments. The increase on recurvatum is best reported as the heel height off the examining table. *Varus stress test at 0° and 30° - Varus stress testing is accomplished while the patient is lying supine on an examination table. The physician supports the thigh against the side of the exam table and applies a varus force to the knee joint while holding the ankle or foot, first at 0°of flexion and then at 30°. As the knee is stressed, the practitioner should feel for increased gapping at the lateral joint space. Gapping can be graded based on the amount the joint opens under stress; grade I causes pain, but with no gap present, grade II causes some gapping, but a definite endpoint is present, and grade III causes significant gapping with no definite endpoint felt. A negative varus stress test shows no difference between either knee at 0° or 30°. Increased gapping at 0° of flexion typically reflects a serious<unk>  injury with a high probability of accompanying cruciate ligament involvement. Lower grades at 30° are more suggestive of partial tears of the FCL or mid-third lateral capsular ligament, while higher grades indicate complete tears of the FCL and damage to other<unk>  structures. *Dial Test<unk>  rotation test) - The dial test can be performed with a patient lying supine or prone. With the patient supine and the knees flexed 30° off the table, stabilize the thigh and externally rotate the foot. As the foot rotates, watch for external rotation of the tibial tubercle of the affected knee compared to the healthy one. A difference of greater than 10-15° indicates a positive test and likely<unk>  to the<unk>  knee. Next, repeat the test with the patient's knees flexed at 90°. Increased rotation at 90° indicates a combined PCL and<unk>  knee injury. If the rotation decreases compared to 30°, then an isolated PLC injury has occurred. Beware of a possible medial knee injury in the face of a positive dial test.<unk>  Drawer Test - The<unk>  drawer test is similar to the commonly known posterior drawer test for PCL stability. Have the patient lie on their back with the knee flexed at 90° and externally rotate the foot to approximately 15°. While stabilizing the foot, apply a<unk>  rotation force to the tibia and watch for the amount of<unk>  rotation. Increased mobility and<unk>  rotation compared to the contralateral normal side usually indicates an injury to the popliteus complex. *Reverse Pivot Shift Test - The reverse pivot shift test is almost exactly as its name implies, a reverse of the pivot shift test. The patient lies on their back with their knee flexed to between 45° and 60° and their foot externally rotated. The practitioner applies a valgus force while slowly extending the knee. A clunk will be felt around 30° of knee flexion if the subluxed or dislocated joint has reduced. This occurs as the iliotibial band changes from a knee flexor to extensor around 30°. Again, the affected knee should be compared the normal side to rule out a false positive test. * Lachman & Posterior drawer tests - Increased anterior translation on the Lachman test is found when the patient has suffered a combined ACL and PLC injury. Increased posterior translation on the posterior drawer test indicates a combined posterior cruciate ligament tear with the PCL injury. *Figure 4 Test - The patient lies supine and flexes their affected knee to approximately 90° then crosses it over the normal side with the foot across the knee and the hip externally rotated. The practitioner applies a varus stress on the joint by pushing the affected knee towards the exam table. This places tension on the<unk>  structures of the knee, especially the popliteus complex and popliteomeniscal fascicles. If these structures have been disrupted by injury, there is no tension to stabilize the lateral meniscus and the lateral meniscus can displace medially into the joint causing the patient pain and reproducing their symptoms at the lateral joint line. As always, the injured knee should be compared to the contralateral normal side. Gait analysis Patients with knee<unk>  suspected to involve the<unk><unk>  should have their gait observed to look for a varus thrust gait, which is indicative of these types of<unk> . As the foot makes contact with the ground, the compartments of the knee should remain tight and stabilize the joint through the impact and movements of walking. In<unk> , the lateral compartment has lost all or part of its stability and cannot maintain normal anatomic positioning when stressed. A varus thrust gait occurs as the foot strikes and the lateral compartment opens due to the forces applied on the joint. This forces the joint to sublux into a varus position to compensate. In chronic<unk> , patients sometimes learn to walk with a partially flexed knee to alleviate the instability caused by their injury. Patients with medial compartment arthritis can also demonstrate a varus thrust gait, so it is important to differentiate between the two causes using plain radiographs. Patients with PLC<unk>  will have increased lateral gapping on varus stress radiographs, while arthritis patients have no gapping but should show signs of joint space narrowing, subchondral cysts, osteophytes, and/or sclerotic bone changes. Arthroscopy Arthroscopy is another useful tool to diagnose and assess<unk>  to the<unk><unk> . Arthroscopy is useful in two ways. First, a patient undergoing arthroscopy is placed under anesthesia which allows for a complete physical examination using the specialized tests described above, which can be difficult with the patient awake. A prospective study that looked at 30 patients undergoing arthroscopy found all of them to have a positive "drive through sign" during evaluation. A drive through sign occurs when there is more than 1 cm of lateral joint opening when a varus stress is applied to the knee which allows the surgeon to easily pass the arthroscope between the lateral femoral condyle and tibia . Second, arthroscopy allows the surgeon to visualize individual structures in the<unk>  knee. The specific structures that can be evaluated are the popliteus tendon attachment on the femur, the popliteomensical fascicles, the coronary ligament of the posterior horn of the lateral meniscus, and the meniscofemoral and meniscotibial portions of the mid-third lateral capsular ligament. Examination of these structures
Posterolateral corner injuries
Retrolisthesis
Tennis injuries
Dural tear
Avulsion fracture
Jones fracture
Greenstick fracture
Rolando fracture