A Brief Synopsis of AFP's "Evaluation of Patients Presenting with Knee Pain:Part I. History, Physical Examination, Radiographs, and Laboratory Tests"

Evaluation of Patients Presenting with Knee Pain:Part I. History, Physical Examination, Radiographs, and Laboratory Tests
WALTER L. CALMBACH, M.D., University of Texas Health Science Center at San Antonio, San Antonio, Texas MARK HUTCHENS, M.D., University of Texas at Austin, Austin, Texas
Am Fam Physician. 2003 Sep 1;68(5):907-912.
http://www.aafp.org/afp/2003/0901/p907.pdf

     When a patient presents with knee pain, determining the type of pain (onset, location, duration, severity, quality, aggravating and alleviating factors) is the first step. If the knee locks, it could be due to a meniscal tear. Popping can be a ligament problem. If the knee "gives way", the cause could be due to a patellar subluxation or ruptured ligament.
     Specific trauma to the knee can help determine the type of injury. Patients who hurt their knee during a head on automobile collision (such as where the knee hits the dashboard) can damage the PCL. The specific force in this situation is an anterior blow to the proximal tibia. A sports injury (or similar action) that puts force on the lateral knee in a lateral-to-medial vector can damage the MCL. Any kind of pain caused from quick pivoting, tight turns, stopping, or non-contact trauma can damage the ACL.
     The physical exam begins with comparing the bad knee with the good knee.  Special attention should be give to looking for swelling, bruising, redness, and discoloration. Range of motion should be checked as well (normally 135 degrees of flexion). Having the patient contract their quads during knee palpation will help assess for proper patella tracking. Measuring the Q angle (using the lines from the ASIS to the patella and the patella to the tibial tuberosity) can help assess patellar subluxation.
     There are several orthopedic tests that should be added to the physical exam in a patient complaining of knee pain. The patellar apprehension test will detect patella subluxation when the physician puts lateral traction on the kneecap.  The anterior and posterior drawer test checks the ACL and PCL, respectively. With the patient supine and the bad leg flexed 30 degrees at the knee, the lower leg can be pulled anteriorly (to check the ACL) and pushed posteriorly (to check the PCL). In the valgus and varus stress test, the clinician simply abducts or adducts the lower leg to check the MCL or PCL, respectively. The McMurray test assesses the medial and lateral menisci. The patient is supine, with the hip and knee flexed at right angles. The lower limb is either externally or internally rotated while the knee is fully flexed. The clinician can also add some valgus stress while the leg is externally rotated or varus stress with internal rotation. A positive test will be pain at the location of the medial or lateral menisci.
     Whether or not to get x rays can be determined by using the Ottawa Knee Rules. The test requires at least one of the following to recommend xrays;
1. age 55 years or older
2. isolated patellar tenderness
3. fibula head tenderness
4. inability to flex the knee past 90 degrees
5. inability to bear weight on the knee and take four steps immediately and in the ED
if x rays are recommended, the AP, lateral, and merchants views should be taken. Young adults may need additional views to look for osteochondritis. Radiographs are used to find fractures or OA.
     If the joint is warm, tender, fluid filled, or red, lab work (CBC w/diff and ESR) and an arthrocentesis may need if septic arthritis or inflammatory arthropathy is suspected. Hemarthrosis may be seen in a ligament tear or fracture.