Knee Injury Basics for the Physician Assistant Exam
Clinically, many health professionals see problems with knees in the older population. The Physician Assistant Exam (PANCE) will cover this common ailment. One of the most common causes is osteoarthritis. The more weight that a person is carrying, the more pain the person can feel and the more difficult walking can be.
Remember that many of the rheumatologic conditions, such as gout and rheumatoid arthritis, can affect the knee.
Osgood-Schlatter syndrome, which predominantly affects adolescent males, is an irritation of the patellar tendon at the tibial tubercle, or tibial tuberosity. Recall that the patella attaches the quadriceps to the tibial tubercle. Repeated stress causes small fractures along the patella tendon. In addition to chronic inflammation, this syndrome can cause changes in the tibial tubercle, including edema, pain, and increased bone growth.
Any type of strenuous activity can precipitate pain. The diagnosis of Osgood-Schlatter syndrome is made on physical examination. Radiograph findings can be variable.
The treatment is usually supportive, and it includes RICE (rest, ice, compression, and elevation). Stretching is key, especially for the quadriceps and hamstring muscles.
The menisci are cartilaginous components that act to provide support for the knee during any type of valgus or varus stress. In the knee, you have both lateral and medial menisci. Tears to the medial menisci are more common.
You often hear about meniscal tears in the knees of professional athletes, especially basketball and football players. Think about the various medial and lateral stresses placed on the knee during a game, and you can easily see why these tears occur.
The affected person may say he or she feels pain on the affected side of the knee (that is, the lateral aspect of the knee if there’s a lateral meniscus tear). As with most knee injuries, you see swelling and edema and pain on palpation. The patient also has trouble bearing weight on the affected side.
For the PANCE, make the connection between meniscal tears and McMurray’s test. In this maneuver, the knee is first flexed; with the opposite hand, a force is directed to stress the knee either medially or laterally. If you hear a clicking sound on the affected side when you begin to extend the leg, the test is positive. Pain can also be induced on the affected side.
The diagnosis of a meniscal tear is confirmed by an MRI. The treatment involves rest, refraining from strenuous physical activity, anti-inflammatory meds, and pain meds. Depending on the degree of meniscal tear, the patient may need arthroscopic surgery.
Ligaments in the knee include the anterior cruciate ligament (ACL) and posterior cruci-ate ligament (PCL). In addition, you have the medial collateral ligament and lateral collateral ligament.
Although you often hear about injuries related to an ACL tear in professional male athletes, ACL tears are actually more prevalent in women. The ACL tear is associated with a tear in the medial menisci, because both tears are caused by a twisting or sharp rotation of the knee.
As with meniscal tears, the person with an ACL tear reports having felt a pop before he or she went down. The pain can be excruciating, and bearing weight can be impossible.
An MRI is needed to evaluate the ACL. The treatment can range from nonsurgical to surgical, depending on the person’s age and the stability of the ligament. Conservative treatment consists of rest, temporarily refraining from strenuous physical activity, and taking anti-inflammatory meds and pain meds.
There’s a triad of knee injuries that orthopedic providers don’t like to see. Called everything from the terrible triad to the unhappy triad to O’Donoghue’s, this triad consists of an ACL tear, a medial meniscus tear, and injury to the medial collateral ligament. In review studies done in the early 1990s, it was — fortunately — not found to be extremely common.
Tears to the posterior cruciate ligament are a lot less common than tears to the ACL because the PCL is a lot stronger and can withstand a lot more punishment. Its main function is to keep the tibia and femur in line. Injuries can occur when an anterior force is directed to a hyperextended knee or a posterior force is directed to a knee in the flexed position.
With mild injuries, range of motion is preserved, and there may not be a lot of swelling over the joint. The posterior drawer test can aid in the diagnosis of a PCL tear, and the diagnosis is confirmed by an MRI. Treatment includes intense physical therapy and rehabilitation.
Collateral ligament tears
Concerning the collateral ligaments, the medial collateral ligament (MCL) is the most commonly injured knee ligament. On physical examination, you test for possible injury to the MCL with a valgus stress test.
Radiographs may be initially obtained to rule out a fracture of the nearby anatomy, especially the femur. The diagnosis is confirmed with an MRI. The treatment consists of rehabilitation for mild tears; note that if the ACL and/or medial menisci have been injured as well, then surgical intervention is needed.
Lateral collateral ligament tears are extremely uncommon. They’re caused by an extreme varus stress on the knee. An MRI is the confirmatory test of choice. Mild tears are usually treated conservatively.
Which of the following is used to diagnose an anterior cruciate ligament (ACL) tear?
(A) Phalen’s maneuver
(B) Lachman test
(C) McMurray’s test
(D) Barlow’s maneuver
(E) Ortolani’s maneuver
The answer is Choice (B), the Lachman test. Note that an anterior drawer test that can also be used to assess for an ACL tear; however, this test isn’t as sensitive or specific as the Lachman test. Phalen’s maneuver is used in diagnosing carpal tunnel syndrome. McMurray’s test is used in diagnosing meniscus tears. Choices (D) and (E) are used to test for congenital hip dislocations, not ACL tears.