Age / Sex : 27 / M

Chief complaint: Right knee pain (badminton athlete)

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Two weeks later, you can see the final diagnosis with a brief discussion of this case.

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Courtesy: Sung Gyu Moon, Konkuk University Hospital

jumper`s knee, chronic patellar tendinopathy

Discussion

Findings:

Plain radiograph demonstrates thickening of the patellar tendon with dystrophic ossification.

Sagittal MR images demonstrate tendon thickening with areas of intratendinous intermediate high signal intensity, peritendinous edematous changes within Hoffa's fat pad, focal bone marrow edema in patella inferior pole. Axial fat-saturated T2W image demonstrate extensive areas of high signal within the patellar tendon and edematous changes within Hoffa's fat pad.

Differential Diagnosis:

Diagnosis:  

jumper`s knee, chronic patellar tendinopathy

Discussion:

Jumper’s knee is an overuse disease. The initial subjective complaints are well-localized pain, usually occurring after physical activities and often at the lower pole of the patella.  Athletes who participate in activities that demand repetitive, violent contraction of the quadriceps musculature are at risk, with basket ball players, volleyball players, cyclists, and runners being most frequently affected. The changes that occur with shearing of the tendinous fibers from repeated microtrauma can progress to significant degeneration and increase the risk of tendon rupture.

Patellar tendinopathy occurs after repetitive microtrauma caused by tendon overload without adequate repair. The diagnosis of patellar tendinopathy is based primarily on clinical examination. It typically affects the deep posterior portion of the patellar tendon adjacent to the lower pole of the patella, although involvement of the tibial insertion of the patellar tendon can occur.

The characteristic imaging findings of patellar tendinopathy on MR imaging are best appreciated on sagittal images, which are focal increase in signal on T2-weighted sequences in the deep posterior portion of the tendon adjacent to the lower pole of the patella, alteration in the tendon size, which primarily affects the proximal posterior and medial fibers, indistinct margins of the tendon, especially posterior to the thickened segment, and patellar marrow changes. Quadriceps muscle atrophy frequently accompanies chronic symptoms.

El-Khoury and colleagues suggested an anteroposterior diameter cutoff point of 7 mm between symptomatic and asymptomatic tendons. Pathologic thickening that is diagnostic of patellar tendinosis characteristically involves the proximal one third of the tendon, and the area of thickening is frequently limited to the medial portion of the proximal tendon. One potential explanation for the asymmetric involvement is that repetitive contraction of the extensor mechanism musculature is unequal because of the lower insertion and larger cross-sectional mass of the vastus medialis muscle compared with the vastus lateralis muscle, which results in the medial portion of the patellar tendon sustaining more tension than its lateral portion. 

Areas of abnormal signal intensity on MR imaging corresponded to degenerative pathologic changes consistent with angiofibroblastic tendinosis and hyaline degeneration.

References:

O'Keeffe SA1, Hogan BA, Eustace SJ, Kavanagh EC. Overuse injuries of the knee. Magn Reson Imaging Clin N Am. 2009 Nov;17(4):725-39