Abstract: A prosthetic implant is disclosed comprising: a first component comprising a first inner surface and a first outer surface, a second component comprising a second outer surface adapted to contact and engage with the first inner surface, the second component further comprising a second inner surface, a third component comprising a third outer surface adapted to contact and engage with the second inner surface, the third component further comprising a third inner surface, and a fourth component comprising a fourth outer surface adapted to contact and engage with the third inner surface; wherein the second component is rotatable relative to the first component about a first axis, the third component is rotatable relative to the second component about a second axis perpendicular to the first axis, and the fourth component is rotatable relative to the third component about a third axis perpendicular to the first axis and second axis; the first inner surface and the second outer surface are each formed with a first

Abstract: A seal arrangement includes a plurality of seal elements arranged in series. At least one seal element has a predetermined rated pressure and includes a relief arrangement permitting relief of pressure across the seal element at a predetermined level lower than said rated pressure.