University of Iowa Family Practice Handbook, Fourth Edition, Chapter 16

Orthopedics: Knee Pain

The majority of knee injuries in adults are of a ligamentous nature. In children, however, a bloody effusion after injury frequently indicates bony injury.

1. Determination of Radiographs. Only 5% to10% of persons with knee trauma have a fracture. Guidelines have been established to hep determine who should have a radiograph. Use clinical judgment, however.
   1. Ottawa Knee Rules. 97% sensitive and 27% specific for fracture. X-ray those who
      1. Are age 55 or older
      2. Have tenderness at head of fibula
      3. Have isolated tenderness of patella
      4. Have inability to flex knee to 90 degrees
      5. Have inability to walk four weight-bearing steps in the ED
   2. Pittsburgh Decision Rules. 99% sensitive and 60% specific for fracture
      1. Blunt trauma or fall as mechanism of injury plus either of the following
      2. Age >55 or <12 years old or
      3. Inability to walk four weight bearing steps in the ER
2. Ligamentous Injuries.
   1. Collateral ligament injury
      1. Typically caused by direct trauma to the contralateral side of the knee, or excessive indirect force to the knee in a varus or valgus manner.
      2. Pain and a tearing sensation may have been noted by the patient at the time of injury. In case of medial collateral ligament injury, there may be tenderness along the distal femur extending to the joint line. Medial collateral ligament injuries are more commonly associated with meniscus tears.
      3. Valgus and varus tests provide assessment of the collateral ligaments. With the knee in 30 degrees of flexion, the collateral ligaments can be isolated.
      4. Grade I sprains are caused by micro-tears of the ligament and correspond to less than 5 mm of increased joint opening and no instability. Grade II sprains are a partial macro-tear of the ligament with the presence of instability and significant increased joint opening with a point. A grade III sprain is a complete tear of the ligament with no end point distinguishable on examination.
      5. Treatment of isolated grade I and II injuries involves conservative measures, such as ice application for 15 to 20 minutes TID and elevation for the first 24 to 72 hours, crutches with limited weight bearing, rest with an immobilizer or hinged brace for 7 to 14 days, and NSAID therapy. Lateral ligament requires 4-6 weeks of a brace. Prompt initiation of physical therapy should be included in initial treatment. Grade III injuries can be treated nonoperatively, but an orthopedic referral is recommended to assess the need for surgical intervention.
   2. Anterior cruciate ligament injury
      1. There is a history of a twisting injury accompanied by a pop or tearing feeling and a subsequent effusion. A hemarthrosis is found in 75% of cases. Frequently associated with a medial collateral ligament injury.
      2. The Lachman and pivot shift tests are useful. The Lachman test is performed with the knee at 30 degrees in a supine position and involves anterior displacement of the tibia on the femur. The pivot shift test involves flexion of the knee while the lower leg is internally rotated and a valgus stress is applied with thumb on lateral knee where a palpable click is felt with extension. Treatment should be supervised by an orthopedist. Treatment of acute injuries depends on the severity. Patients without associated meniscal, collateral ligament, or posterior cruciate ligament injury should be treated by immobilization of the knee for comfort and crutches. Patients with associated ligament injury or meniscal injury should be referred immediately to an orthopedist because surgery may be necessary. Often leads to OA if untreated.
   3. Posterior cruciate ligament injury.
      1. Most injuries are the result of direct trauma to the proximal tibia when the flexed knee is decelerated rapidly, as in a dashboard injury.
      2. The posterior drawer and tibial sag tests are used. In the posterior drawer test, the knee is flexed 90 degrees and posterior displacement of the tibia on the femur is attempted. In the tibial sag test, the knee is flexed to 90 degrees with hip at 45 degrees, the tibia is displaced posteriorly on the femur.
      3. Isolated tears should be managed conservatively with physical therapy and quadriceps strengthening. If radiographs reveal displaced bony avulsions, posterior cruciate ligament injury may require surgical fixation. Orthopedic referral is recommended.
3. Meniscal Tears.
   1. Clinical features.
      1. Meniscal injuries are a common cause of knee joint pain. The median meniscus more frequently injured than is the lateral. More than one third of meniscal injuries are associated with an anterior cruciate ligament tear and possibly medial collateral ligament injuries.
      2. Patients complain of pain at the time of injury, which persists and interferes with weight-bearing activity. The most consistent physical finding is tenderness to palpation along the joint line. Patients often complain of the knee "locking," which may be attributable to pain or a physical inability to extend the knee because the torn meniscus prevents extension.
      3. Several clinical tests help determine if meniscal injury is present. In the McMurray’s test, the knee is fully flexed, with the leg externally rotated when one is testing for medial meniscal tears and internally rotated when testing for lateral meniscal tears. While maintaining rotation, extend the knee with a firm controlled movement. A painful click signifies a positive test. The Apley’s test is performed with the patient in a prone position. The knee is flexed to 90 degrees, and an axial load is placed on the heel of the foot while the lower leg is rotated internally and externally. If pain results, the test is positive.
   2. Diagnosis. If there are any diagnostic doubts, patients should be referred for evaluation by magnetic resonance imaging or arthroscopy.
   3. Treatment. The knee should be immobilized if there is pain with motion. Crutches, quadriceps exercises, and NSAIDs can be used. If the knee remains locked or if symptoms of pain, giving way (a sense that the knee is going to collapse), and swelling persist, orthopedic referral should be made for surgical intervention.
4. Patellofemoral Pain Syndrome.
   1. Clinical features. Most common anterior knee problem seen by the family physician. The problem presents as anterior knee pain, which is worse after prolonged sitting with the knee flexed, or on climbing or descending stairs or slopes. Patients may complain of some snapping, popping, or crepitus about the patella.
   2. Radiographs of the knee are usually negative. However, lateral displacement of the patella on a Merchant view may be present.
   3. Treatment. NSAIDs, ice application, and appropriate exercises including those that strengthen the medial quadriceps and stretch the hamstrings are useful (such as straight leg raising with the ankle and hip externally rotated).
5. Patellar Dislocations.
   1. Clinical features. Patients complain of the knee giving way or popping out. The patella may still be dislocated when patient is seen, but many spontaneously reduce. An effusion (hemarthrosis) may be present. The medial retinaculum is tender. Apprehension test: displace the patella laterally; patients feel as though the patella is going to dislocate and will be very apprehensive. Between occurrences the patella is observed to have considerable lateral mobility, particularly during active extension. The patellar ligament may be noted to angulate laterally from the axis of the quadriceps muscle.
   2. Reduction. Encourage the patient to relax the quadriceps and push the patella medially back into place. If unable to get the patella over the lateral femoral condyle, push the patella anteriorly while passively flexing the knee (the patella usually reduces by 30 degrees of flexion). If the effusion is tense, aspiration may reduce discomfort.
   3. Postreduction care. Adequate immobilization is obtained with the use of a knee immobilizer for 6 weeks. Have patients fully weight bearing as well as performing quadriceps isometric exercises while immobilized. After immobilization, patients are placed on partial weight bearing while quadriceps strengthening is initiated. Rehabilitation needs to include the vastus medialis, which operates only in the last 15 degrees of extension. Resume full weight bearing when flexion to 30 degrees is painless. An elastic knee support may add some patellar stability during strenuous activity. Dislocation more than three times may require surgical treatment.
6. Prepatellar Bursitis. See olecranon bursitis section.

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See related Provider Topics Bones, Joints and Muscles, Injuries and Wounds or Knee Injuries and Disorders.

See related Patient Topics Bones, Joints and Muscles, Injuries and Wounds or Knee Injuries and Disorders.

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