Knee Soft Tissue Injury (ACL, LCL, MCL, PCL) Management in the ED

Soft tissue knee injuries are some of the most common and clinically challenging musculoskeletal disorders seen in the emergency department. Accurate and timely diagnosis increases the likelihood of fully restoring normal and pain-free use of the affected knee. Knee pain and related symptoms may derive from damage to one or more of the soft tissue structures that stabilize and cushion the knee joint (including the ligaments, muscles, tendons, and menisci), from infection to the knee joint or surrounding structures, or from trauma to the bones forming the joint. In addition to the etiology of the patient's presenting symptom, determine the acuity of the pathologic process as an acute traumatic or infectious event or exacerbation of a chronic overuse or degenerative syndrome. ^{[1, 2, 3, 4, 5]}

Accurate and timely diagnosis increases the likelihood of fully restoring normal and pain-free use of the affected knee. For most patients, the severity of the etiology and the injury or pathologic process, acute or chronic, can be determined from a targeted history, focused physical examination, and thoughtful workup including diagnostic imaging (eg, plain radiography).

(The image below depicts the normal anatomy of the knee.)

Signs and symptoms

The history should focus on the following:

• Confirming that an acute traumatic event occurred
• Documenting the mechanism of injury (including the circumstances of the injury)
• Assessing the stability of the joint
• Determining the type and location of the pain
• Evaluating the onset and degree of knee effusion
• Assessing joint mobility (eg true locking vs pseudolocking)

The initial physical examination focuses on inspection, palpation, and neurovascular evaluation. Steps that may be useful include the following:

• Observation of the patient’s stance and gait, if possible
• Inspection of the knee
• Ballottement of the patella
• Measurement of the Q angle
• Inspection and palpation of the popliteal fossa
• First and second Steinmann signs
• Payr sign
• Patellar apprehension sign
• Palpation of the anterior aspects of both thighs (in quadriceps rupture)
• Palpation of the relevant bursae (in bursal injuries)
• In children, palpation of the epiphyses
• Range-of-motion (ROM) testing
• Lachman maneuver
• Anterior and posterior drawer tests
• Tibial sag test
• Pivot-shift test
• McMurray test
• Apley compression test
• Thessaly and Ege tests

Diagnosis

The following laboratory studies may be helpful:

• Blood typing and screening
• Complete blood count (CBC)
• Erythrocyte sedimentation rate (ESR)
• Serum electrolytes
• Blood glucose
• Blood urea nitrogen (BUN) and creatinine
• Analysis of aspirated synovial fluid for white blood cell (WBC) count and differential and for glucose and protein levels

Plain radiographs are recommended for the following scenarios ^{[2, 6]} :

• Patients older than 55 years
• Patients with tenderness over the fibular head
• Patients with discomfort confined to the patella upon palpation
• Patients unable to flex the knee to 90°
• Patients incapable of bearing weight, immediately and in the ED, for at least 4 steps

Other diagnostic procedures that may be helpful are as follows:

• MRI ^{[7, 6, 8, 9, 10, 11, 12]}
• Ultrasonography ^{[6, 13, 14, 15]}
• Arteriography (when a knee dislocation is strongly suspected) ^{[2, 16]}
• Injection of methylene blue
• Knee joint aspiration

Management

General treatment principles include the following:

• Aside from the particular injury, treatment depends on the patient’s age and activity level and the presence of additional injuries
• Obtain orthopedic consultation when appropriate
• Initial nonpharmacologic treatment includes rest, ice, compression, and elevation (RICE)
• For the first 1-3 days, use therapeutic measures that minimize incipient damage and reduce pain and inflammation
• Consider splinting the injured knee to provide support and to prevent further injury
• Serviceable devices include immobilizers and handcrafted compressive dressings
• Detrimental effects of immobilization include joint stiffness, degenerative changes in articular cartilage, muscle atrophy and weakness, and decreased vascularity

Therapy for specific injuries include the following:

• For first-degree sprains, provide symptomatic treatment (essentially RICE); normal function usually returns quickly
• Second-degree sprains must be protected by using a cast, cast brace, or a restrictive movement brace; arrange for timely follow-up care
• Treatment of third-degree sprains depends on the severity and type of instability; some third-degree sprains of ligaments call for surgical repair
• Treatment for anterior cruciate ligament (ACL) injuries is individualized, influenced by the presence or absence of comorbid pathology, age of the patient, baseline activity level, degree of instability, and associated ligamentous injuries miring the knee
• Presence of a meniscal tear does not automatically lead to surgical intervention; if the knee is not locked or unstable, conventional treatment (ie, RICE) ordinarily suffices

Reduction of knee dislocation includes the following:

• Most knee dislocations reduce spontaneously before arrival in the ED; however, when findings suggest neurovascular compromise, attempt to restore circulation with traction or reduction and emergency orthopedic consultation
• Classify dislocations with respect to the relationship of the tibia on the femur
• Anterior dislocations occur most commonly
• Ideally, perform reductions in the operating room with general anesthesia; however, if circumstances preclude this scenario, an attempt in the ED is warranted
• Barring contraindications, administer conscious sedation
• With an assistant providing stabilization and countertraction of the thigh, a second person applies longitudinal traction to the leg; this usually suffices for reduction.
• Reduction of an anterior dislocation may be aided by transposing the femur anteriorly
• Avoid affixing pressure over the popliteal space; this may exacerbate arterial damage
• For posterior dislocations, attempt to reinstate the tibia anteriorly
• After relocation, confirm neurovascular status and immobilize the knee in 15° of flexion
• Order postreduction images and consultation with the orthopedic surgeon, and obtain an emergency arteriogram

Reduction of patellar dislocation includes the following:

• Patellar dislocations typically occur in predisposed individuals and tend to recur
• Patellar dislocations are identified with respect to the patella’s position on the knee joint, with lateral dislocations being most common
• If the joint has not reduced spontaneously, verify the dislocation radiographically
• After administering necessary analgesia, place the hip in a mild amount of flexion, and gently press anteriorly and medially on the patella while extending the knee joint
• Postreduction films should include a sunrise view
• Other types of patellar dislocations tend to be resistant to closed reduction
• Aspiration of a Baker cyst may render temporizing relief

Pediatric cases

In any child with a traumatic injury, be alert to the possibility of child abuse.

Children with hip disorders, especially a slipped capital femoral epiphysis and Legg-Calvé-Perthes disease, may have referred pain to the knee. Ligamentous damage, meniscal damage, and dislocations (with the exception of patellar dislocations) are rare in children.

Children with open epiphyseal plates may have injuries that can be mistaken for soft tissue injuries.

The missing of growth-plate injuries in children may result in deformity and growth irregularities. If the patient has circumferential tenderness about the lower part of the femur or the proximal tibia, treat it as a Salter-Harris growth-plate injury, even if radiography findings are normal.

Impetuous stress testing of the knee joint may induce additional damage, displacing a fracture or worsening a growth-plate disturbance.

A completely displaced epiphyseal fracture of the distal femur is the pediatric equivalent of adult knee dislocation. This injury may also harm the popliteal artery.

Osteochondritis dissecans, an intra-articular disorder of unclear etiology, is most common in boys during late childhood or in male adolescents. The condition is characterized by degeneration and recalcification of the articular cartilage and underlying bone. Patients tend to report vague, poorly localized knee pain, as well as morning stiffness or recurrent effusions. Osteochondritic lesions can be radiographically occult, and CT, bone scanning, or MRI may be required to make the diagnosis.

Although not strictly a disease, Osgood-Schlatter disease probably originates from microtrauma, leading to apophysitis at the insertion of the patellar tendon into the tibial tubercle.

Complaints of knee pain generally start in energetic children aged 9-15 years, a time of rapid growth.

Discomfort tends to be localized, and palpation reveals swelling and tenderness over the tibial tubercle.

Boys are affected more commonly than girls; activity exacerbates pain, and bilateral involvement occurs in about 30% of patients.

Initial treatment is conservative, with activity limited to the patient's tolerance.

Geriatric cases

Rupture of the extensor mechanism may precede trivial trauma in the elderly, especially in individuals with coexisting disorders, such as renal failure, systemic lupus erythematosus, hyperparathyroidism, or diabetes mellitus.

Because of underlying degenerative disease, meniscal tears may emerge in older patients with a history of minimal or no trauma. For example, simply rising from a squatting position may cause a tear.

Discomfort and distention related to the knee after a fall may arise from a fracture of the tibial plateau, especially the lateral plateau.

Osteoporosis, commonly occurring in elderly persons, makes bones more vulnerable to fracture. Visualization of fractures on plain images is difficult, and fractures may be easily overlooked. Misdiagnosing this fracture as a soft tissue injury may lead to additional morbidity, as fracture fragments may be displaced.

Pregnancy

Knee problems, especially underlying meniscal and patellar problems, may worsen with pregnancy because of changes in the biomechanics of weight bearing and shifting in the center of gravity with fetal development.

Production of relaxin hormone during pregnancy may modify ligaments of the knee, in addition to those of the pelvis, increasing knee laxity.

Radiography in pregnancy is always a concern. Although some risk is associated with obtaining diagnostic radiographs in pregnancy, animal and human data do not reveal an increased risk to the fetus when fetal exposure is limited. After 20 weeks' gestation, the risk of radiation exposure that might cause fetal abnormalities is remote; however, avoid unessential radiography. If radiographs are deemed indispensable, shield the patient's abdomen.