Age / Sex : 46 / F

Chief complaint : Left knee pain for 1 week

What is your diagnosis?

Two weeks later, you can see the final diagonosis with a brief discussion of this case (Please submit only one answer).

Courtesy : Kyung Ah Chun, Catholic Kwandong University, International St. Mary’s Hospital

Discussion

Answer:  

Calcific tendinitis (calcium hydroxyapatite deposition disease), biceps femoris tendon on fibular attachment

Findings:

Plain radiograph shows a well-defined, ovoid shaped, calcified mass over left fibular head.

MRI shows intratendinous calcified mass of low signal intensity at the fibular attachment of biceps femoris with diffuse biceps femoris muscle and lateral subcutaneous edema.

Differential Diagnosis:

Heterotopic ossification

Gout tophi

Soft tissue chondroma

Discussion:

Periarticular calcific tendinitis is an inflammatory condition associated with calcium hydroxyapatite crystal deposition disease processes. The shoulder is most commonly involved, but has also been seen in the hip, elbow and wrist joints. Hydroxyapatite crystals may deposit in the tendons, ligaments, joint capsule, soft tissues or bursae. Calcific deposits around the knee have been described involving the lateral collateral ligament, vastus lateralis and popliteus tendons.

The radiographic appearance of the crystal deposits reflects the duration of disease: initially, the crystals appear poorly defined and cloudlike, but as the disease progresses, they appear denser and homogeneous with a linear or circular configuration. MRI shows extensive edema in the muscle and adjacent bone marrow as high T2 signal intensity.

References:

1. Chan W, Chase HE, Cahir JG, Walton NP. Calcific tendinitis of biceps femoris: an unusual site and cause for lateral knee pain. BMJ Case Rep 2016. doi:10.1136/bcr-2016-215745


2. Anderson SE¹, Bosshard C, Steinbach LS, Ballmer FT. MR imaging of calcification of the lateral collateral ligament of the knee: a rare abnormality and a cause of lateral knee pain.

AJR Am J Roentgenol. 2003;181(1):199-202.