Ligament Balancing in Total Knee Arthroplasty Section 2 | Functional properties of the ligaments

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2.0 – Fundamentals of ligament function Overview [Fig 2.0.1] Deformities in osteoarthritis of the knee can lead to contracted ligaments on the concave side and to elongated ligaments on the convex side.

2.0 – Fundamentals of ligament function Short ligaments versus long ligaments [Fig 2.0.2] Classification of ligaments into short ligaments and long ligaments.

2.0 – Fundamentals of ligament function Characteristics of short ligaments [Fig 2.0.3] Short ligaments stabilize throughout the whole range of motion.

2.0 – Fundamentals of ligament function Characteristics of long ligaments [Fig 2.0.4] Long ligaments stabilize only in parts of the range of motion.

2.0 – Fundamentals of ligament function Ligament characteristics in healthy, osteoarthritic, and replaced knees. [Fig 2.0.5] Deformities in osteoarthritis of the knee can lead to contracted ligaments on the concave side and to elongated ligaments on the convex side.

2.1 – Ligaments and dynamic stabilizers of the medial aspect of the knee Deep medial collateral ligament (deep MCL) [Fig 2.1.1] The range of stabilizing properties of the deep MCL: 0–120°

2.1 – Ligaments and dynamic stabilizers of the medial aspect of the knee Posteromedial corner and semimembranosus muscle [Fig 2.1.2] The range of stabilizing properties of the posteromedial corner and the semimembranosus tendon: 0–45° (up to 60°).

2.1 – Ligaments and dynamic stabilizers of the medial aspect of the knee Superficial medial collateral ligament (superficial MCL) [Fig 2.1.3a] Ranges of stabilizing properties of the superficial MCL (anterior fibers: 20–120°; posterior fibers: 0–20°)

2.1 – Ligaments and dynamic stabilizers of the medial aspect of the knee Superficial medial collateral ligament (superficial MCL) [Fig 2.1.3b] The relation of the fibers’ origin to the transepicondylar axis determines their function. In full extension the posterior structures are tight and the anterior structures are loose.

2.1 – Ligaments and dynamic stabilizers of the medial aspect of the knee Superficial medial collateral ligament (superficial MCL) [Fig 2.1.3c] In slight flexion both anterior and posterior fibers are tight.

2.1 – Ligaments and dynamic stabilizers of the medial aspect of the knee Superficial medial collateral ligament (superficial MCL) [Fig 2.1.3d] In flexion the anterior structures are tight and the posterior structures are loose.

2.1 – Ligaments and dynamic stabilizers of the medial aspect of the knee Pes anserinus group [Fig 2.1.4] The range of stabilizing properties of the pes anserinus group: 0–20°.

2.2 – Ligaments of the dorsal aspect of the knee Posterior cruciate ligament [Fig 2.2.1a] The PCL is a moderate secondary stabilizer against valgus stress. It has special importance when the primary medial stabilizers like the MCL have been released.

2.2 – Ligaments of the dorsal aspect of the knee Posterior cruciate ligament [Fig 2.2.1b] The range of stabilizing properties of the pes anserinus group: 0–20°.

2.2 – Ligaments of the dorsal aspect of the knee Posterior capsule [Fig 2.2.2a] The range of stabilizing properties of the posterior capsule: 0–10° (up to 20°).

2.2 – Ligaments of the dorsal aspect of the knee Posterior capsule [Fig 2.2.2b] The posterior capsule is a strong varus/valgus stabilizer in full extension.

2.2 – Ligaments of the dorsal aspect of the knee Posterior capsule [Fig 2.2.2c] The posterior capsule slackens in early flexion losing stability.

2.3 – Ligaments and dynamic stabilizers of the lateral aspect of the knee Iliotibial band (ITB) [Fig 2.3.1a] The range of stabilizing properties of the ITB: 0–90°.

2.3 – Ligaments and dynamic stabilizers of the lateral aspect of the knee Iliotibial band (ITB) [Fig 2.3.1b] The ITB has an anterior and a posterior portion. Posterior structures are tight in extension.

2.3 – Ligaments and dynamic stabilizers of the lateral aspect of the knee Iliotibial band (ITB) [Fig 2.3.1c] Anterior structures are tight in flexion. Due to the additional fibers to the patella, the ITB is held anteriorly across the axis of rotation and is also a (weaker) stabilizer in flexion.

2.3 – Ligaments and dynamic stabilizers of the lateral aspect of the knee Popliteal tendon [Fig 2.3.2a] The femoral attachment of the popliteal tendon lies distally and slightly anteriorly to the axis of rotation (lateral epicondyle representing the transepicondylar axis). In extension the tendon is slightly slack.

2.3 – Ligaments and dynamic stabilizers of the lateral aspect of the knee Popliteal tendon [Fig 2.3.2b] In increasing flexion the femoral attachment of the popliteal tendon is moved in a proximal and anterior direction, thus tightening the tendon.

2.3 – Ligaments and dynamic stabilizers of the lateral aspect of the knee Popliteal tendon [Fig 2.3.2c] The range of stabilizing properties of the popliteal tendon: 30–120°.

2.3 – Ligaments and dynamic stabilizers of the lateral aspect of the knee Lateral collateral ligament (LCL) [Fig 2.3.3a] The range of stabilizing properties of the LCL: 0– 120°.

2.3 – Ligaments and dynamic stabilizers of the lateral aspect of the knee Lateral collateral ligament (LCL) [Fig 2.3.3b] The LCL is a short ligament, tight in full extension.

2.3 – Ligaments and dynamic stabilizers of the lateral aspect of the knee Lateral collateral ligament (LCL) [Fig 2.3.3c] Due to a certain amount of lateral roll-back in flexion, the posterior part of the LCL tends to be slightly looser. This does not occur in a regular total knee arthroplasty due to reduced rollback.

2.3 – Ligaments and dynamic stabilizers of the lateral aspect of the knee Posterolateral corner and lateral gastrocnemius tendon [Fig 2.3.4a] The tendon of the lateral gastrocnemius muscle runs perpendicularly to the joint line, thus giving a certain restraint against varus stress, especially in extension.

2.3 – Ligaments and dynamic stabilizers of the lateral aspect of the knee Posterolateral corner and lateral gastrocnemius tendon [Fig 2.3.4b] The lateral gastrocnemius tendon provides restraint against varus stress in flexion, but this weakens beyond 90° of flexion.

2.3 – Ligaments and dynamic stabilizers of the lateral aspect of the knee Posterolateral corner and lateral gastrocnemius tendon [Fig 2.3.4c] The range of stabilizing properties of the posterolateral corner and the tendon of the lateral gastrocnemius muscle: 0–90° (up to 120°).

2.3 – Ligaments and dynamic stabilizers of the lateral aspect of the knee Biceps femoris [Fig 2.3.5a] The range of stabilizing properties of the biceps femoris: 0–10° (up to 20°).

2.3 – Ligaments and dynamic stabilizers of the lateral aspect of the knee Biceps femoris [Fig 2.3.5b] The biceps femoris runs posteriorly to the flexion/extension axis. It functions as a stabilizer in full extension.

2.3 – Ligaments and dynamic stabilizers of the lateral aspect of the knee Biceps femoris [Fig 2.3.5c] The biceps femoris does not stabilize from early flexion onward.

2.3 – Ligaments and dynamic stabilizers of the lateral aspect of the knee Posterior cruciate ligament and posterior capsule [Fig 2.3.6] The range of stabilizing properties of the PCL: 0–120°; posterior capsule: 0–10° (up to 20°).