Event coverage is one of the key responsibilities of the team physician. Acute knee injuries are one of the most common injuries requiring on-lhe-field evaluation.1 The team physician and medical staff must be prepared to perform an accurate and rapid evaluation of the acute knee injury. The sideline evaluation includes a focused history and comprehensive knee examination. Of paramount importance is the ability to identify injuries that require prompt evaluation and treatment in a setting other than the sideline. An expeditious history and physical exam by an appropriately prepared physician will identify any injuries such as fractures or dislocations that may require further treatment in an emergency room.
HISTORY AND PHYSICAL EXAMINATION
The goal of the initial onthe-field examination is to perform a quick evaluation of the injury, address any unstable fractures or dislocations, and safely transfer the athlete to the sidelines. The sideline physical examination of the acutely injured knee should be rapid, complete, and systematic. The examination should always begin with observation of the limb for deformity, lacerations, skin dimpling, swelling, and ecchymosis. Palpation of all bony and softtissue structures about the knee may reveal tenderness, crepitation, or step-off s . The knee should be checked for an acute hemarthrosis and range of motion within the athlete's tolerance. Loss of range of motion may be secondary to pain, large effusion, or mechanical block. The leg and thigh compartments must be examined for signs of increased pressure. A complete neurovascular examination must be preformed.
EXTENSOR MECHANISM INJURIES
Extensor mechanism injuries can include dislocation of the patellofemoral joint, quadriceps or patellar tendon rupture, and patella fractures. Injuries can occur either through direct blow or following a maximum eccentric load to the patellofemoral joint.2
Disruption of the quadriceps or patella tendon usually occurs from application of a maximal eccentric load. Quadriceps tendon rupture usually occurs in patients aged >40 years while patella tendon rupture occurs in patients aged <40 years. Risk factors for tendon rupture include chronic tendonopathy, steroid use, and chronic metabolic disorders.3 Predisposing factors for patella dislocation include abnormal lower extremity alignment and history of previous dislocation.
Examination will reveal pain referred to the anterior aspect of the knee. There may be immediate soft-tissue swelling, particularly with patella dislocation, which usually produces a large hemarthrosis within hours. Palpation of the extensor mechanism may reveal focal tenderness, obvious gaps, or marked patella alta or baja. Integrity of the extensor mechanism can be checked by having the athlete perform a straight leg raise. Presence of an extensor lag or inability to do a straight leg will confirm disruption. Spontaneously reduced patella dislocation will frequently be associated with patella apprehension.
Figure 1: Photograph of the right knee showing the "dimple" sign.
If the patella remains dislocated a reduction should be performed by manually reducing the patella medially towards the trochlear groove while simultaneously gently extending the knee.
Sideline treatment of extensor mechanism injuries should include immobilization in extension, ice, compression, and elevation. The athlete should be kept on crutches with protected weight bearing. The athlete should be referred to an orthopedic surgeon for repeat examination, plain radiographs, and definitive treatment plans.
Compared with acute softtissue injuries, sports-related knee fractures are rare.4 Although these injuries are uncommon, medical personnel on the sideline should suspect, evaluate, and provide initial management when they occur. Potential injuries include distal femur, patella, proximal tibia, and osteochondral fractures. In juvenile athletes, distal femoral and proximal tibial physeal fractures, pateliar sleeve fractures, and intercondylar eminence avulsions are possible.
Periarticular knee fractures usually occur as a result of axial compression associated with varus and valgus loading.5 Patella fractures may occur as a result of a direct anterior blow or forceful contraction of the extensor mechanism. Fractures may be associated with gross limb malalignment. The knee must be inspected closely for abrasions, ecchymosis, lacerations, swelling, and hemarthrosis. Systematic palpation of all bony prominence may elicit areas of focal tenderness or crepitance. A careful neuro vascular examination and assessment of compartment swelling should be performed.
Immediate treatment should include reduction of any gross malalignment. If a fracture is suspected based on history and examination, the knee should be immobilized to prevent further fracture displacement or soft-tissue injury. Any associated soft-tissue wounds should be covered with a sterile dressing. Cryotherapy should be initiated to minimize swelling. Once stabilized, the athlete should be expeditiously transferred to a location where formal radiographie examination and fracture stabilization are available.
ACUTE UGAMENTOUS INJURY
Sideline personnel will be frequently called on to evaluate the knee with an acute ligamentous injury. Ligamentous injuries may occur in isolation or in combination depending on the mechanism. Key elements to obtain during history taking include whether the injury involved contact, position of the leg, direction of contact, a "pop" sensation, and instability.
Figura 2: AP radiograph shows tibiofsmoral joint subluxation.
Initial examination should focus on skin inspection, evaluation for hemarthrosis, and identifying areas of focal tenderness. A gentle range of motion examination should be performed. Inability to fully extend the knee may indicate a displaced bucket handle meniscal tear or osteochondral fragment. A complete systematic examination of stability in all planes should be conducted acutely before soft-tissue swelling and patient guarding inhibit diagnostic ability. All examinations for instability should be compared to the uninjured side. Stability should be graded based on the degree of laxity and the presence or absence of a firm endpoint.
The medial collateral ligament (MCL) is the most commonly injured ligament about the knee.6 An isolated MCL injury usually occurs from a valgus blow to the leg. The entire course of the MCL should be palpated for areas of focal tenderness. The MCL injury should be graded according to the amount of opening to a valgus stress at 30° of flexion. Opening to valgus stress in full extension implies injury to a second major stabilizer. Isolated varus loads to the knee resulting in isolated injury to fibular collateral ligament are rare. Any fibular collateral ligament injury with varus instability should be considered a "kneedislocation" with appropriate evaluation and transfer to an emergency room.
The anterior cruciate ligament (ACL) is the primary stabilizer to anterior tibial displacement. Common noneontact mechanisms of injury are sudden deceleration and rotational maneuvers. The most sensitive test for an ACL injury is the Lachman test.7 With the knee flexed 30°, an anterior directed force is applied on the proximal tibia while holding the femur with the other hand. Additionally an anterior drawer and pivot shift tests should be performed.
The posterior cruciate ligament (PCL) is the primary stabilizer preventing posterior displacement of the tibia on the femur. Examination for a PCL injury should begin with examining the position of the tibia in relationship to the femur. This can be done by examining the medial tibial plateau, which should sit 10 mm anterior to the medial femoral condyle. Checking the relative position of the tibia prior to stability testing can prevent falsely attributing anteroposterior laxity to a torn ACL. The most accurate test for detecting a PCL injury is the posterior drawer test at 90° of flexion.8
Figure 3: Coronal MRI shows medial collateral ligament rupture with displacement into the medial joint space.
Rotational stability should be examined to assess for injuries to the posterolateral ligamentous complex. Tibial external rotation or "dial" test should be done at 30° and 90° of knee flexion. The anterior and posterior drawer tests should be repeated with the tibia externally rotated. Increased external rotation at 90° of knee flexion, as well as increased translation with drawer testing in external rotation implies a combined cruciate and posterolateral injury.
Treatment of acute ligament injuries depends on the grade of injury. Athletes with grade I tears may be considered for return to play. If examination shows a firm end-point with no or minimal instability, the athlete should undergo a sideline functional evaluation to help determine playing status. If the athlete shows appropriate response to sideline functional testing, as described below, consideration can be given for return to play.
Treatment for higher-grade isolated ligament injuries should begin on the sideline with ice and compressive dressings. The leg may be placed in a hinged knee brace for additional support. The athlete should maintain protected weight bearing with crutches. The athlete should be advised to continue cryotherapy and watch for signs of neurovascular injury until follow-up.
ACUTE MULTIPLE LIGAMENT INJURY
A suspected knee dislocation or multiple-ligament injured knee represents an "orthopedic emergency." A thorough and expethent physical examination must be performed with particular attention to the neurovascular status of the extremity. Although the majority of knee dislocations occur following high-energy trauma, medical personnel must be aware that they also occur during participation in level 1 athletics.9 The risk of vascular injury following knee dislocations is between 10% and 64%.30
Examination should begin with observation of the entire extremity. Inspection should note any ecchymosis, lacerations, or deformity. The presence of a dimple sign or tight compartments should be assessed. Although some knee dislocations present with obvious deformity, the majority of multiple-ligament injured knees spontaneously reduce. A detailed neurovascular examination should follow inspection. The popliteal, dorsalis pedis, and posterior tibial pulses are palpated and compared with the normal leg. Sensation and motor function of the tibial and peroneal nerves should be checked.
A dislocated knee should undergo an on-field reduction attempt. Reduction is done with the application of gentle longitudinal traction. The presence of a skin dimple may imply the need for open reduction. After reduction, a repeat neurovascular examination should be performed, A complete evaluation of all ligamentous structures should be performed.
Following complete evaluation and any necessary reduction, sideline management should consist of immobilization in extension and commencement of cryotherapy. The athlete should immediately be referred to a tertiary care center where orthopedic and vascular surgeons are available. Radiographs of the knee will confirm anatomic joint reduction and any fractures. Evaluation of possible vascular injuries associated with knee dislocations remains controversial, but may include close observation, ankle-brachial index measurements, ultrasound venography or angiography."
A 51 -year-old man sustained a twisting injury to his right knee while playing soccer. No medical personnel were in attendance for an on-field evaluation. Examination revealed marked soft-tissue swelling and ecchymosis. Figure I shows a lateral patella subluxation, prominence of the media! femoral condyle, and dimpling of the skin over the medial joint-line. He had 3+ instability to valgus stress in full extension, positive Lachman, and posterior drawer tests. Neurovascular examination was normal.
Plain radiographs revealed subluxation of the libiofemoral joint with widening of the medial joint space (Figure 2). Magnetic resonance imaging demonstrated femoral avulsion of the superficial MCL with displacement into the medial joint space. The patella was laterally subluxated with associated disruption of the medial patellofemoral ligament. The ACL and PCL were also torn (Figure 3).
The patient underwent open reduction of the posterolateral knee dislocation. Intraoperatively, the medial femoral condyle was found buttonholed through the medial retinaculum. The tibiofemoral and paíeílofemoraJ joints were reduced. The medial patellofemoral and MCL avulsions were repaired. Eight weeks later the patient underwent ACL and PCL reconstruction.
Appropriate sideline management of this patient would have involved identifying the multipleligament injured knee, thorough neurovascular examination, immobilization, and immediate referral to a tertiary emergency department.
RETURN TO PLAY
Return-to-play is the process of deciding when an injured athlete may safely return to practice or competition. The decision should be made with input from the player, coaches, athletic trainers, and physicians. The health and safety of the patient, potential risk to other participants, functional capabilities of the patient, and functional requirements of the sport should be considered.12
If no specific soft-tissue or bony injury is diagnosed after an acute knee injury despite an appropriate history and examination, the athlete can be considered for return to play. Under the guidance of an athletic trainer and physician, a functional evaluation of the athlete should take place on the sidelines. Functional evaluation of the injured knee includes range of motion, manual muscle testing, double leg and single leg hops, running, and changing directions. This should be followed by position-specific/sport-specific functional testing.
Ii' the symptoms improve and the athlete shows acceptable functional capacity, a return to play can be considered. The athlete who returns to play should be closely observed by the medical personnel and coaching staff. If the symptoms recur or the level of play is deemed unacceptable by the coaching staff, a repeat examination should take place.
Sideline management of acute knee injuries requires medical personnel to have knowledge of injury patterns, mechanisms, physical findings, and treatment strategies. Fractures and multiple-ligament injured knees need to be rapidly diagnosed and stabilized to allow for timely transfer to a location where further evaluation and definitive treatment can be provided.
1. Bollen S. Epidemiology of knee injuries: diagnosis and triage. Br J Sports Med. 20(K); 34:227-228.
2. Bharam S, Vrahas MS, Fu FH: Knee fractures in the athlete. Orthap Clin North Am. 2002; 33:565-74.
3. Maffulli N. Wong J. Rupture of the Achilles and patellar tendons. Clin Sports Med. 2003; 22:761-176.
4. Cohn SL, Sotta RP, Bergfeld JA. Fractures about lhe knee in sports. Clin Sports Med. 1990: 9:121-139.
5. Hipp JA. Hayes WC. Biomechanics of Fractures. In: Browner BD. Jupiter JB, Levine Am, Trafton PG, eds. Skeletal Trauma. Philadelphia. Pa: WB Saunders; 1998:97130.
6. Felto JF. Marshall JL. Medial collateral ligament injuries of lhe knee: a rationale for treatment. Clin Onhop. 1978; 132:206-218.
7. Mitsou A, Valtianalos P. Clinical diagnosis of ruptures of the anterior cruciate ligament: u comparison between the Lachman test and the anterior drawer sign. Injury, 1988; 19:427-428.
8. Rubinstein RA Jr, Shelbourne KD, McCarroll JR, VanMeter CD. Rettig AC. The accuracy of the clinical examination in the setting of posterior cruciate ligament injuries. Am J Spons Med 1994; 22:550-557.
9. Brautigan B, Johnson DL. The epidemiology of knee dislocations. CUn Sports Med. 2000; 19:387-397.
10. Cole BJ. Harner CD: The multiple ligament injured knee. CUn Sports Med. 1999; 18:241262.
11. Armstrong PJ, Franklin DP: Treatment of vascular injuries in the multiple-ligamentinjured knee. Operative Techniques in Sports Medicine. 2003: 11:199-207.
12. McFarland EG. Return to play. Clin Sporn Mea. 2004; 23:svxxiii.