Achilles tendon and miscellaneous tendon lesions.
Abnormalities of the tendons of the foot and ankle are quite common and their number seems to be increasing. Commonly involved tendons include the Achilles and peroneal tendons; the tibialis anterior and flexor hallucis longus tendons are involved less commonly. Magnetic resonance imaging is well suited to imaging these abnormalities. It is a noninvasive modality that uses no ionizing radiation. It has the capability of imaging in any plane, which is well suited to imaging the tendons of the ankle because their course is not in standard orthogonal planes. MR imaging provides excellent soft tissue contrast and is well able to differentiate the tendons from surrounding fat as well as to detect the presence of hemorrhage and edema. Abnormalities of these tendons include complete and partial tears as well as tendinitis and tenosynovitis. These abnormalities are usually secondary to trauma or to mechanical irritation or synovial inflammation. They can be diagnosed routinely and confidently by MR imaging. Complete tears may be seen as a discontinuity within the substance of a tendon with interposed edema or hemorrhage. Partial tears may be seen as increased signal within a tendon that extends to a surface. Tendinitis is manifested by thickening of the tendon with intratendinous signal that does not extend to its surface.