Tear of the peroneus longus tendon can be difficult to diagnose and tr
eat. Fourteen cases of clinically proven tears are reported. Patients
ranged in age from 31 to 63 years. There were 10 men and four women. T
he onset of symptoms was acute in eight cases. Chronic onset with slow
ly increasing pain occurred in six cases. Despite acute onset of sympt
oms, only one patient was diagnosed within 2 weeks of his injury. The
others had symptom duration ranging from 7 to 48 months. Twelve tears
were located distally as the tendon turned into the cuboid groove. An
os peroneum visible on x-ray was present in six cases, absent in seven
cases, and cartilaginous in one case, The os peroneum was involved in
the tear in three cases, Excision of part or all of the os peroneum w
as performed in four cases with a bridging tendon graft required in on
e case. A plantaris tendon graft was required in one case in which an
os peroneum was absent. Patients with acute onset of symptoms tended t
o fare better than those with chronic onset of symptoms, regardless of
the length of time from onset to time of surgery. Associated patholog
y in the peroneus brevis tendon was common, occurring in nine cases. T
hese patients seemed to have a better surgical outcome than those with
only a tear of the peroneus longus tendon. Associated findings affect
ed diagnosis by masking symptoms but did not alter the outcome of trea
tment. The presence or absence of an os peroneum did not affect sympto
ms or treatment, but its presence on x-rays may aid in the diagnosis i
f migration of part or all of the sesamoid occurs.