The palmaris longus muscle is a variable muscle. The most common variation is its absence. Several in vivo and in vitro studies have documented the prevalence of absence of the PL tendon in different ethnic groups. Between 5. 5 and 24% of Caucasian populations (European and North American) and 4. 6 to 26. 6% of Asian populations (Chinese, Japanese, Indian, Turkish, Malaysian) have been reported to lack the PL tendon.