Posterior cruciate ligament The gold standard for diagnosing tears in the posterior cruciate ligament (PCL) is the posterior drawer test.11,12 Use the same position and stabilize the patient in the same way as for the anterior drawer test. Palpate along the medial and lateral anterior joint lines with your thumbs to determine if the tibia translates forward; wrap your hands around the tibia and push forward. Increased laxity compared with that of the uninvolved knee indicates PCL insufficiency.
The reverse pivot shift is used to evaluate PCL insufficiency with a posterolateral corner injury. With the patient supine on the examination table, hold the patient's leg flexed to 45°. Rotate the tibia outward, apply inward pressure on the tibia, and move the knee into full extension. A positive finding is confirmed by an audible and/or palpable clunk as the leg is fully extended.
An additional method for diagnosing PCL insufficiency is the posterior sag test. With the patient supine on the examination table, flex the hip and the knee to 90° (see Figure 8). If the tibia subluxates or sags below the femur, the finding is positive for PCL insufficiency.
Posterolateral corner This complex combination of soft tissue structures is located along the posterior and lateral aspect of the knee. The key anatomic elements are the LCL, the popliteus tendon, the popliteofibular ligament, and the posterolateral joint capsule.13 An isolated injury to the posterolateral corner is rare; it usually occurs in combination with a ligament injury or knee dislocation. The posterolateral corner must be evaluated if an ACL tear is diagnosed because an injury requires immediate repair or reconstruction. ACL reconstruction will ultimately fail if the posterolateral corner injury is missed.
The dial test evaluates posterolateral corner insufficiency. This test is best performed with the patient prone with the knees together. Rotate the tibias outward at both 30° and 90° flexion (see Figure 9). A positive finding is an increased rotation of more than 10° to 15° on the involved leg. Increased rotation at only 30° flexion indicates an isolated posterolateral corner injury; increased rotation at both 30° and 90° indicates a posterolateral corner injury and PCL insufficiency.14-16
Patellofemoral joint A positive finding on the patella grind test reproduces the patient's pain and indicates that the patient has patellofemoral-related pathology. With the patient's leg in full extension, push the patella down and toward the femur as the patient contracts the quadriceps muscles. The Q angle, also called the quadriceps angle, is the difference between the alignment of the femur from the iliac spine to the patella and the alignment of the tibia from the patella to the tibial tubercle (see Figure 10). In men, the Q angle is 10º; in women, 15°.17 A greater angle is indicative of patella malalignment.18-20 The J sign is used to evaluate patella tracking. A positive finding is pathognomonic for lateral patella subluxation.17 The patient sits at the end of the exam table with the knee flexed 90°. As the patient fully extends the knee, the examiner watches the movement of the patella. A positive J sign occurs when the patella slides laterally as the leg approaches full extension.21
Extensor mechanism The quadriceps tendon, the patella, and the patella tendon make up the extensor mechanism of the knee.22 Ruptures of the quadriceps or patella tendon can have a detrimental outcome if not diagnosed acutely. Quadriceps tendon ruptures typically occur in persons older than 40 years, whereas patella tendon ruptures typically occur in younger persons.11 These ruptures tend to occur with an eccentric contraction of the knee. Patients may hear a pop, are usually unable to walk after the injury, and develop a large knee effusion. Examination findings are a palpable suprapatellar gap if the quadriceps tendon is ruptured and a palpable infrapatellar gap if the patella tendon is ruptured.23 A person who ruptures either of these tendons is unable to perform a straight leg raise or extend the knee.22 These patients must be referred to an orthopedic surgeon immediately.
NEUROVASCULAR EXAMINATION
All extremity examinations must include a neurovascular evaluation. The vascular examination is performed by palpating pulses distal to the knee, including the posterior tibialis and the dorsalis pedis pulse. Capillary refill should occur in less than 2 seconds.
The neurologic examination involves evaluating both sensory and motor functions. Sensation is evaluated over the L2-S2 dermatomes. A decrease in sensation over a particular dermatome is a positive finding. Motor testing is performed to assess the function of nerves L2-S2. Knee extension is used to evaluate the femoral nerve; knee flexion, the sciatic nerve; plantar flexion of the foot, the tibial nerve; and dorsiflex and an outward turn of the foot, the peroneal nerve. An evaluation of the patella (L4) and Achilles (S1) deep tendon reflexes completes the neurovascular examination. An inability to perform any of the motor test maneuvers is a positive finding for a knee injury. In addition, strength can be graded using the 5/5 muscle-grading system.
CONCLUSION
Knee injuries are one of the most common reasons for a patient visit with a primary care provider. Acute or chronic knee pain also results in millions of patient visits each year. All clinicians should know how to perform a complete knee examination. Consistent use of a systematic knee examination allows PAs to be more confident in their ability to diagnose knee problems. A thorough knee history leads to an appropriate differential diagnosis, and a comprehensive physical examination leads to an accurate diagnosis. A discussion of treatment options can begin promptly. The patient will be grateful to know what is wrong, and treatment is more effective with timely initiation or prompt referral to an orthopedic surgeon. JAAPA
Kerri Browne is a staff physician assistant in the Department of Orthopaedic Surgery, Bone and Joint/Sports Medicine Institute, Naval Medical Center Portsmouth, Portsmouth, Virginia. Christopher Kurtz is assistant professor of surgery, Uniformed Services University of the Health Sciences, and vice chairman, Department of Orthopaedic Surgery, Bone and Joint/Sports Medicine Institute, Naval Medical Center Portsmouth. They have indicated no relationships to disclose relating to the content of this article.
The views expressed in this article are those of the authors and do not reflect the official policy or position of the Department of the Navy, the Department of Defense, or the United States Government.
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