A system for controlling a relationship between first and second bodies (12, 14) on a person, the system comprising: a suture assembly comprising at least a first suture configured to define a restrictable loop structure with the suture assembly in an operative state, the restrictable loop structure comprising at least first and second restrictable sub-loops (20a', 20b') that cooperatively define a first loop that can be reduced in size to thereby produce a force on the first and second bodies (12, 14) that urges the first and second bodies (12, 14) towards each other, the first and second restrictable sub-loops (20a', 20b') respectively being made up of first and second loop lengths (CLA, CLB), the first loop length having a first sliding portion with the second loop length having a second sliding portion, the suture assembly being configured to define at least one knot that extends around the first and second sliding portions, the suture assembly being configured so that the first and second sliding portions upon each being moved within the at least one knot in a tightening sliding direction cause a size of a respective sub-loop (20a', 20b') to be reduced, the suture assembly further being configured so that tensioning of the loop, as caused by urging the first and second bodies (12, 14) away from each other with the suture assembly in the operative state, causes separate first and second circumferential lengths (CLA, CLB) of the first loop to be drawn away from the at least one knot, the suture assembly being configured so that drawing of each of the first and second circumferential lengths (CLA, CLB) of the first loop away from the at least one knot causes the at least one knot to grasp at least one of the first and second sliding portions with a greater force that opposes enlargement of at least one of the sub-loops (20a', 20b') and thus an effective size of the first loop by resisting movement of at least one of the first and second sliding portions within the at least one knot in a direction opposite to the tightening sliding direction, characterized in that the at least first knot comprises first and second knots (24a', 24b') and the first loop length defines one of the first and second knots (24a', 24b') and the second loop length defines the other of the first and second knots (24a', 24b'). a suture assembly comprising at least a first suture configured to define a restrictable loop structure with the suture assembly in an operative state, the restrictable loop structure comprising at least first and second restrictable sub-loops (20a', 20b') that cooperatively define a first loop that can be reduced in size to thereby produce a force on the first and second bodies (12, 14) that urges the first and second bodies (12, 14) towards each other, the first and second restrictable sub-loops (20a', 20b') respectively being made up of first and second loop lengths (CLA, CLB), the first loop length having a first sliding portion with the second loop length having a second sliding portion, the suture assembly being configured to define at least one knot that extends around the first and second sliding portions, the suture assembly being configured so that the first and second sliding portions upon each being moved within the at least one knot in a tightening sliding direction cause a size of a respective sub-loop (20a', 20b') to be reduced, the suture assembly further being configured so that tensioning of the loop, as caused by urging the first and second bodies (12, 14) away from each other with the suture assembly in the operative state, causes separate first and second circumferential lengths (CLA, CLB) of the first loop to be drawn away from the at least one knot, the suture assembly being configured so that drawing of each of the first and second circumferential lengths (CLA, CLB) of the first loop away from the at least one knot causes the at least one knot to grasp at least one of the first and second sliding portions with a greater force that opposes enlargement of at least one of the sub-loops (20a', 20b') and thus an effective size of the first loop by resisting movement of at least one of the first and second sliding portions within the at least one knot in a direction opposite to the tightening sliding direction, characterized in that the at least first knot comprises first and second knots (24a', 24b') and the first loop length defines one of the first and second knots (24a', 24b') and the second loop length defines the other of the first and second knots (24a', 24b').