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Emergency and Acute Medicine – Patellar Injuries
Patellar injuries encompass a spectrum of conditions involving the patella and its associated extensor mechanism, including patellar dislocation, patellar fracture, patellar tendon rupture, and patellar tendinitis. These injuries commonly result from traumatic forces, sudden deceleration, or repetitive overuse and are frequently encountered in athletic and emergency settings. Accurate recognition is essential, as management ranges from conservative treatment to urgent surgical intervention.
Patellar dislocation most often occurs due to sudden knee flexion combined with external rotation of the tibia on the femur, accompanied by a strong contraction of the quadriceps muscle. Lateral dislocation is by far the most common type, with the patella displaced over the lateral femoral condyle. Direct trauma to the patella is a less frequent cause. Risk factors include genu valgum, patella alta, shallow femoral trochlea, weak vastus medialis, pes planus, and structural abnormalities of the patella. Dislocations are particularly common in adolescent athletes, especially females, and younger age at first dislocation is associated with higher recurrence rates.
Patients with patellar dislocation typically report a sensation of the knee “giving way,” often accompanied by a popping or tearing feeling, immediate pain, swelling, and difficulty bearing weight. On examination, there may be an obvious lateral deformity of the patella, although spontaneous reduction frequently occurs before ED evaluation. Tenderness along the patella and a positive apprehension test (Fairbanks sign) are characteristic findings.
Patellar fractures are most commonly caused by direct trauma such as a fall or direct blow to the knee, often resulting in comminuted or minimally displaced fractures. Indirect mechanisms involve excessive tension through the extensor mechanism, leading to transverse or displaced fractures. Transverse fractures account for the majority of cases, followed by comminuted, longitudinal, and osteochondral fractures. Patients present with anterior knee pain, swelling, hemarthrosis, difficulty ambulating, and impaired knee extension. Palpable defects or crepitus may be present.
Patellar tendon rupture usually results from a forceful eccentric contraction of the quadriceps on a flexed knee, such as during landing from a jump or heavy lifting. It occurs more often in older athletes and in patients with predisposing conditions such as chronic patellar tendinitis, diabetes mellitus, inflammatory arthropathies, prior steroid injections, or previous knee surgery. Clinically, patients experience abrupt severe pain, inability to maintain knee extension, and a high-riding patella on examination or imaging.
Patellar tendinitis, also known as “jumper’s knee,” is an overuse injury caused by repetitive microtrauma from activities involving frequent jumping or rapid acceleration and deceleration. It is common in volleyball players, basketball players, runners, and high jumpers. Patients typically report localized pain at the inferior pole of the patella or proximal patellar tendon that worsens with stair climbing or rising from a seated position.
Radiographic evaluation is essential in suspected patellar injuries. Standard anteroposterior, lateral, and sunrise (axial) views of the knee should be obtained. In patellar dislocations, postreduction radiographs are important to exclude associated osteochondral fractures. A bipartite patella may mimic fracture and should be distinguished with comparison views if needed. In patellar tendon rupture, imaging may reveal a superiorly displaced patella. Radiographs are often normal in early patellar tendinitis.
Management depends on the specific injury. Simple lateral patellar dislocations are typically reduced by gentle knee extension, sometimes with medial pressure on the patella. Procedural analgesia or sedation may be required. Other dislocation types (superior, medial, or intra-articular) should not be reduced in the ED and require orthopedic consultation. Patellar fractures warrant orthopedic evaluation; nondisplaced fractures with intact extensor function may be treated nonoperatively with immobilization, while displaced or open fractures require surgical management. Patellar tendon rupture requires early orthopedic consultation and surgical repair, typically within two to six weeks. Patellar tendinitis is managed conservatively with rest, activity modification, NSAIDs, and physical therapy.
Patients with successfully reduced lateral patellar dislocations and normal postreduction imaging may be discharged with a knee immobilizer, crutches, and close orthopedic follow-up. Admission is indicated for irreducible dislocations, associated fractures, open injuries, or compromised extensor mechanism. Important clinical pearls include recognizing that patellar dislocations may spontaneously reduce prior to evaluation and that swelling may obscure a palpable defect in patellar tendon rupture.
Patellar injuries encompass a spectrum of conditions involving the patella and its associated extensor mechanism, including patellar dislocation, patellar fracture, patellar tendon rupture, and patellar tendinitis. These injuries commonly result from traumatic forces, sudden deceleration, or repetitive overuse and are frequently encountered in athletic and emergency settings. Accurate recognition is essential, as management ranges from conservative treatment to urgent surgical intervention.
Patellar dislocation most often occurs due to sudden knee flexion combined with external rotation of the tibia on the femur, accompanied by a strong contraction of the quadriceps muscle. Lateral dislocation is by far the most common type, with the patella displaced over the lateral femoral condyle. Direct trauma to the patella is a less frequent cause. Risk factors include genu valgum, patella alta, shallow femoral trochlea, weak vastus medialis, pes planus, and structural abnormalities of the patella. Dislocations are particularly common in adolescent athletes, especially females, and younger age at first dislocation is associated with higher recurrence rates.
Patients with patellar dislocation typically report a sensation of the knee “giving way,” often accompanied by a popping or tearing feeling, immediate pain, swelling, and difficulty bearing weight. On examination, there may be an obvious lateral deformity of the patella, although spontaneous reduction frequently occurs before ED evaluation. Tenderness along the patella and a positive apprehension test (Fairbanks sign) are characteristic findings.
Patellar fractures are most commonly caused by direct trauma such as a fall or direct blow to the knee, often resulting in comminuted or minimally displaced fractures. Indirect mechanisms involve excessive tension through the extensor mechanism, leading to transverse or displaced fractures. Transverse fractures account for the majority of cases, followed by comminuted, longitudinal, and osteochondral fractures. Patients present with anterior knee pain, swelling, hemarthrosis, difficulty ambulating, and impaired knee extension. Palpable defects or crepitus may be present.
Patellar tendon rupture usually results from a forceful eccentric contraction of the quadriceps on a flexed knee, such as during landing from a jump or heavy lifting. It occurs more often in older athletes and in patients with predisposing conditions such as chronic patellar tendinitis, diabetes mellitus, inflammatory arthropathies, prior steroid injections, or previous knee surgery. Clinically, patients experience abrupt severe pain, inability to maintain knee extension, and a high-riding patella on examination or imaging.
Patellar tendinitis, also known as “jumper’s knee,” is an overuse injury caused by repetitive microtrauma from activities involving frequent jumping or rapid acceleration and deceleration. It is common in volleyball players, basketball players, runners, and high jumpers. Patients typically report localized pain at the inferior pole of the patella or proximal patellar tendon that worsens with stair climbing or rising from a seated position.
Radiographic evaluation is essential in suspected patellar injuries. Standard anteroposterior, lateral, and sunrise (axial) views of the knee should be obtained. In patellar dislocations, postreduction radiographs are important to exclude associated osteochondral fractures. A bipartite patella may mimic fracture and should be distinguished with comparison views if needed. In patellar tendon rupture, imaging may reveal a superiorly displaced patella. Radiographs are often normal in early patellar tendinitis.
Management depends on the specific injury. Simple lateral patellar dislocations are typically reduced by gentle knee extension, sometimes with medial pressure on the patella. Procedural analgesia or sedation may be required. Other dislocation types (superior, medial, or intra-articular) should not be reduced in the ED and require orthopedic consultation. Patellar fractures warrant orthopedic evaluation; nondisplaced fractures with intact extensor function may be treated nonoperatively with immobilization, while displaced or open fractures require surgical management. Patellar tendon rupture requires early orthopedic consultation and surgical repair, typically within two to six weeks. Patellar tendinitis is managed conservatively with rest, activity modification, NSAIDs, and physical therapy.
Patients with successfully reduced lateral patellar dislocations and normal postreduction imaging may be discharged with a knee immobilizer, crutches, and close orthopedic follow-up. Admission is indicated for irreducible dislocations, associated fractures, open injuries, or compromised extensor mechanism. Important clinical pearls include recognizing that patellar dislocations may spontaneously reduce prior to evaluation and that swelling may obscure a palpable defect in patellar tendon rupture.
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