Are all ligaments of the hip and knee joints taut when these joints go into extension?

Ligament Tension in Hip and Knee Extension

The statement that all ligaments of both the hip and knee joints are taut when those joints go into extension is false. Different ligaments have specific functions and tension patterns that vary with joint position.

Knee Joint Ligaments During Extension

When examining the knee joint ligaments during extension:

• The anterior cruciate ligament (ACL) is taut in maximal extension, serving as a restraint to prevent forward migration of the tibial attachment 1
• The posterior cruciate ligament (PCL) is primarily taut in intermediate positions and maximal flexion, not in extension 1
• The cruciate ligaments contain functionally different fiber groups with varying tension patterns - some fibers are taut in extension while others are not 1

This differential tension pattern is important for proper joint biomechanics. During hyperextension, the ACL restrains forward tibial movement while the PCL works with other structures to prevent posterior joint opening 1.

Hip Joint Ligaments During Extension

The hip joint capsular ligaments show distinct functional patterns:

• The ischiofemoral ligament primarily controls internal rotation in both flexion and extension, not overall extension 2
• The lateral arm of the iliofemoral ligament has dual control of external rotation in flexion and both internal and external rotation in extension 2
• The pubofemoral ligament primarily controls external rotation in extension 2

These ligaments work together to provide stability but are not all uniformly taut during extension.

Clinical Implications

Understanding the selective tension patterns of ligaments is crucial for:

• Proper assessment of joint stability
• Diagnosis of specific ligament injuries
• Planning appropriate rehabilitation strategies

For example, in knee extension, the ACL is under greater tension than the PCL, which becomes more important in flexion 1. Similarly, different hip ligaments have specific roles in controlling rotation rather than all being uniformly taut in extension 2.

Anatomical Considerations

The structure of ligaments reflects their function:

• Cruciate ligaments have varying fiber orientations that allow different portions to be taut in different positions 1
• Hip ligaments show specific directional control rather than uniform tension 2
• The term "isokolyons" describes lines from which fibers showing identical elongation in percentage originate when exposed to force 1

This anatomical arrangement allows for optimal joint stability throughout the range of motion without requiring all ligaments to be taut simultaneously in any one position.