On 14 August 1981, Lienen suffered a severe injury, as Norbert Siegmann of Werder Bremen slit his thigh open with his studs resulting in an open deep wound of 25 cm (10 in), exposing his muscles and femur. The wound required 23 stitches; nevertheless, after just 17 days, Lienen started practicing again.
Born in England to an English father and a Greek Cypriot mother, he began his senior career at Tottenham Hotspur, where he made one substitute appearance in the EFL Cup. He was transferred to Vitria de Guimares in 2024 and was sold to Sporting in January 2024 for an initial 7.67 million.