A Rare Diagnosis and Repeated Knee Injury in a Young Athlete - PowerPoint Presentation

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A Rare Diagnosis and Repeated Knee Injury in a Young Athlete

Author: Anthony

Kohlenberg

, MD

Co-author:

Ketan

Mody

, MD

Editor:

Yaowen

Hu, MD

Case Series Editor: Michael Henehan, DO

History

Patient Presentation:

CC: Right-sided anterior knee pain with activities.

History:

HPI: A 12 year-old male complains of worsening knee pain over the last several months. He denies significant knee trauma. However, he reports an increased physical activity level, including organized basketball and baseball. Additionally, the pain is aggravated when he kneels on the affected side. 4 weeks prior to exam, the patient was diagnosed with Patellofemoral Pain Syndrome but his symptoms did not improve with PT. 

PMH: Periventricular Leukomalacia (PVL), a form of intrauterine brain injury. Diagnosis was confirmed at age 6 with brain MRI

(Photos 1 & 2)showing

a

hyper-intense

lesion of the left periventricular white matter. The patient’s right sided growth and strength have been affected by this

condition.

Photo 1

Photo 2

Physical Exam

General

: The patient is a well-developed, left-handed male with normal body habitus for stated age. 

Inspection:

The right leg has visibly less muscle mass than the left. The right calf circumference measures 29.0cm, the left measures 31.5cm. The right leg measures 1cm shorter than the left. 

Active ROM: Right leg ROM is from 0 to 125 degrees of flexion at the knee. There is anterior knee pain with complete extension. 

Palpation:

There is 2+ tenderness of the inferior patella on the bone, no tenderness of the medial or lateral

peri

-patellar

borders. There is no patellar apprehension and no tenderness on the joint line, MCL, or LCL. 

Strength:

Right leg flexion/extension and foot plantarflexion/dorsiflexion are 4+/5. Respective left sided strength is 5/5. 

Special Testing:

Right leg ligamentous stability tests are unremarkable. 

Neurologic:

Bilateral patellar and Achilles reflexes are 2+/4. 

Gait:

Trace right-sided foot drop and

in-toeing

.

Broad Differential Diagnosis

Patellofemoral Pain Syndrome 

Patellar Tendonitis 

Sinding-Larsen-Johansson Syndrome 

Patellar Contusion 

Infrapatellar Fat Pad Syndrome 

Bipartite Patella 

Patellar Fracture

Question 1

The complaint of bilateral knee pain is most commonly associated with:

A) Patellofemoral syndrome

B) Patellar stress fracture

C) Patellar contusion

D) None of the above

Answer: A

Other Studies

Lab Studies:

None

Other Studies:

Bilateral knee x-rays 4 weeks prior to exam show the right patella measures smaller than the left (3.5 x 2.8cm vs 3.8 x 3.6cm). Further X-rays

(Photo 3) at

that time were negative for

fracture.

MRI right knee

(Photos 4 & 5) shows

complete,

non-displaced

fracture off the inferior pole of the right patella, inferior patella marrow edema, inflammatory changes of the right patellar tendon consistent with stress reaction, absence of edema anterior to the patella that might otherwise have indicated soft tissue

trauma.

Consultations

:

None

Photo 3

Photo 4

Photo 5

Final Diagnosis, Treatment and Outcome

Working Diagnosis:

Stress fracture of the right patella

Treatment:

The patient was braced in extension and remained non-weight bearing for 4 weeks. Through the following 2 weeks, he was limited to walking/ADLs while wearing his protective brace. After 6 weeks of rest, the patient was pain-free and resumed activities/PT as tolerated without bracing.

Outcome:

6 weeks after resuming activities, the patient returned to clinic with recurrent right knee pain. Symptoms occurred suddenly with a sprint out of the batter’s box during a baseball game.

X-ray (Photo 6)

found a new complete,

nondisplaced

fracture of the right inferior patella. 

The patient was once again placed in a protective brace and removed from activities until pain-free. After 4 weeks of rest, x-ray of the right knee

(Photo 7)displayed

healing of the repeat patellar fracture and he gradually weaned off the knee brace, returning to activities as tolerated while completing physical therapy. He has since returned to play without restriction or exacerbation for 7 months. 

Photo 6

Photo 7

Question 2

Stress fractures in which of the following areas are considered to be at high risk of progressing to a complete fracture?

A) Femoral neck

B) Patella

C) Anterior tibia

D) All of the above

Answer: D

Teaching Points – Author’s Comments

Stress fractures of the patella are uncommon in athletes. They typically arise in normal bone that has been exposed to repetitive, excessive stress (fatigue). Less commonly, they can result from abnormal bone structure or density exposed to relatively normal loading (insufficiency), often secondary to iatrogenic insult rather than bone pathology.(1-4) 

Patients generally present with anterior knee pain in the setting of increased activity with limited time for recovery. Symptoms may resolve with rest and immobilization, then come back with resumption of activity.(1,5) 

Radiography is the initial study of choice, but MRI may be required in patients with a high index of suspicion for fracture.(1,6,7) 

Complete

non-

displaced

fractures typically heal with non-operative treatment. This consists of bracing in extension for 4-6 weeks, followed by rehab and gradual return to activities. Generally, patients can be expected to make a full recovery and return to pre-injury levels of activity.(1) 

This patient deviates from the normal course by experiencing a repeat injury. The patient’s right leg sequelae secondary to PVL could be a source of bone insufficiency, and his 7-day-a-week activity level in multiple sports could fatigue the patella. Both of these factors may have predisposed him to further injury. If he were to have failed conservative management, or if the fracture was displaced, he may have required operative treatment.(1) 

Teaching Points – Author’s Comments

A pediatric neurologist diagnosed this patient’s condition at age 6 when right leg weakness/foot drop, decreased right leg length, right toenail hypoplasia, and left-handedness prompted imaging. 

PVL is the predominant form of ischemic brain injury in premature infants. Unlike preterm newborns, the most common pattern of injury in term infants predominantly affects watershed areas of the cerebral cortex.(8-10) Since this patient was born full term without complication, the periventricular insult likely occurred early in the third trimester as in other cases of term infants with PVL.(11-13) 

Preterm infants with PVL are at high risk for spastic

diplegia

, developmental delay, visual impairment, and epilepsy.(11,12,14) PVL in term children represents a distinct clinical entity with developmental delay and heterogeneous motor findings beyond the classic spastic

diplegia

/cerebral palsy. This diagnosis should be considered in patients with developmental or motor abnormalities even in the absence of perinatal complications.(11)

Teaching Points – Editor’s Comments

Patella stress fractures are considered high risk stress fractures. Risk factors include bipartite patella and cerebral palsy. Given this patient's previous neurological condition, it is reasonable to suggest that his decreased VMO size places him at more risk for patella stress fractures. Since the VMO absorbs the majority of the force in the lower extremity and given his slight in-toeing during his gait, the force distribution across the lower extremity may prove to be too much to handle for his smaller patella. Treatment for patella stress fractures are individualized. For displaced fractures or with non-union, ORIF often is required. If the stress fracture is not displaced, conservative therapy including restriction of

activity can be undertaken.

Bracing may be indicated as well.

Question 3

All patellar stress fractures should be treated with open reduction internal fixation (ORIF)

True

False

Answer: False

References

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Surg

59A:934-939, 1977. 

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Orthop

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RR, Greer WJ,

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