Working Diagnosis:
Pre-patellar hematoma/bursitis with an internal degloving injury from a shear mechanism.

Treatment:
Aspiration of the hematoma with an 18 gauge needle, compression bandage, short term immobilization, and an icing regimen.

Outcome:
After four weeks of the prescribed treatment, the patient reported diminished swelling, full range of motion, and a desire to return to sports (basketball). Upon return to strenuous activities, the patient reported a re-aggravation of his symptoms with worsening swelling and pain over the anterior aspect of the knee. Attempts at aspiration at an urgent care facility were unsuccessful. The patient returned for orthopaedic evaluation and aspiration revealed 15cc of bloody fluid from the pre-patellar compartment of the knee. Once again, compression and immobilization were instituted. The patient returned two days later with worsening swelling and significant pain around the knee joint. The patient was scheduled for pre-patellar bursectomy with drain placement. At the time of surgery, evacuation of the hematoma was performed and a drain placed. A complete blood count performed at the time of surgery demonstrated a WBC count of 329,000 and a hemoglobin of 7.5. This test was repeated with similar results and the specimen was reviewed by the hematology team. Several blast cells and immature white blood cells were present in the specimen. The patient was urgently worked up by the pediatric team and transferred for treatment at a nearby children’s hospital after confirmation of the diagnosis of Chronic Myelogenous Leukemia. The patient required two more surgical procedures to reduce the amount of fluid accumulating around the joint while in the pediatric facility. At five weeks post-operative, the patient was responding to oral therapy (tyrosine kinase inhibitor Imatinib) and the swelling was significantly diminished. His second drain, which was placed nearly four weeks prior, was pulled in the office after 24 hour output was less than 10cc. The patient’s wounds ultimately healed without event. At the 10 week follow up the patient had great quad tone, no effusion, and full range of motion with no pain. He also had a slight and still not complete remission of his leukemic condition. At this point he was cleared from an orthopaedic standpoint and able to return to all sport related activities at the discretion of his oncologist.

Author's Comments:
Morel-Lavallée Lesion (MLL) is delamination of the skin and subcutaneous fat from the underlying quadriceps fascia, with rupture of the perforating vessels. Possible findings include large recurrent fluid collections occurring in the potential space created and insidious accumulation of fluid and progressive difficulty with knee flexion.
Hallmark findings:
Suprapatellar area of palpable fluctuance with extension into the thigh.
Evaluation of a contact athlete who suffers a shearing knee injury must include MLL in the DDx; though it must be differentiated from Prepatellar bursitis and Quadriceps contusion.
Delayed diagnosis is not uncommon.
MR Imaging characteristic findings: demonstrates subcutaneous fluid extending to the mid-coronal plane and mid-thigh, beyond the area of the prepatellar bursae.

Treatment goals for MLL about the knee :
Resolution of the fluid collection
Prevention of recurrence
Achievement of full active knee flexion
Return to play

Treatment for concealed degloving injuries of the knee
Small fluid collections with full ROM:
Compression wrapping
Vasopneumatic cryotherapy
immediate motion exercises with an emphasis on knee flexion.
Large fluid collections with loss of ROM:
Attempting up to 3 aspirations as needed
Compression wrapping
Vasopneumatic cryotherapy
If serial aspiration is unsuccessful, sclerodesis can be safely performed.
Delayed treatment may result in bacterial infection of the fluid collection.
Compression wrapping alone has not been shown to be effective compared to aspiration of the fluid collection followed by compressive wrapping.
Minimally invasive surgical drainage is an alternative.
Open drainage can be saved as a last resort given the need for hospitalization, prolonged suction drainage, and an extended treatment course. However, that method has been proven to be effective in the hip region and could theoretically be used in a very extensive MLL of the knee and thigh that was large in size.
Sterile talc sclerodesis, in a similar procedure to talc pleurodesis is a safely and effectively performed surgical option. Both tetracycline and doxycycline have also been safe and highly effective in sclerosis of malignant pericardial effusions and benign lymphoepithelial cysts of the parotid gland, suggesting that application to an MLL could yield similar results.

Editor's Comments:
This is an excellent case of a Morel-Lavallée Lesion (MLL) which more commonly occurs in elite athletes as a result of a high energy injury. Though it’s clear that the authors had a high suspicion of MLL, a more complete description of this patient’s MRI interpretation would be interesting to see, as the MRI is usually essential to confirming diagnosis, and as was so well described in the Authors’ 2nd reference. It's not clear how the concomitant diagnosis of Chronic Myelogenous Leukemia (also known as Chronic Myeloid Leukemia) contributed or predisposed this young athlete (with a seemingly mild traumatic event) to MLL. There was no mention of a low platelet count or other abnormal bleeding parameters but it certainly seems that it could have played a role and the authors wisely demonstrated how important it is to investigate recurrent effusions or areas of swelling that occur or recur without probable cause.
References:
Matava MJ, et al. Morel-Lavallée Lesion in a Professional American Football Player. Am J Orthop. 2010;39(3):144-147.
Vanhegan IS, et al. The Morel-Lavallée Lesion as a Rare Differential Diagnosis for Recalcitrant Bursitis of the Knee: Case Report and Literature Review. Case Rep Orthop. 2012: 593193.
Tefferi A, Vardiman, JW. Classification and diagnosis of myeloproliferative neoplasms: The 2008 World Health Organization criteria and point-of-care diagnostic algorithms. Leukemia. 2008;22:14-22.

Garcia-Manero G, et al. Chronic Myelogenous Leukemia: A Review and Update of Therapeutic Strategies. Cancer. 2003;98(3):437-457.

http://www.mayoclinic.com/health/chronic-myelogenous-leukemia/DS00564/DSECTION=symptoms

References:
1. Harma A, Inan M, Ertem K. The Morel-Lavallee lesion: a conservative approach to closed degloving injuries. Acta Orthop Traumatol Turc. 2004;38:270-273.
2. Mellado JM, Bencardino JT. Morel-Lavall´ee lesion: review with emphasis on MR imaging. Magn Reson Imaging Clin N Am. 2005;13:775-82.
3. Tejwani SG, Cohen SB, Bradley JP. Management of Morel-Lavallee lesion of the knee: twenty-seven cases in the national football league. Am J Sports Med. 2007;35:1162-7. Epub 2007 Mar 9.
4. Tseng S, Tornetta P 3rd. Percutaneous management of Morel-Lavallee lesions. J Bone Joint Surg Am. 2006;88:92-6.

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