Tibial collateral ligament
Ligamentum collaterale tibiale
Also known as: medial collateral ligament, MCL
A broad, flat band on the medial side of the knee from the medial femoral epicondyle to the medial tibia. It resists valgus and external rotation forces and is firmly attached to the medial meniscus.
Overview
The superficial TCL runs from the medial epicondyle of the femur to the medial surface of the tibia ≈5–7 cm below the joint line, deep to the pes anserinus (sartorius, gracilis, semitendinosus tendons). Its deep part is a capsular thickening (meniscofemoral and meniscotibial ligaments) attached to the medial meniscus — the anatomical basis for combined MCL–meniscal injuries. Together with the posterior oblique ligament it is the primary restraint to valgus (abduction) stress and helps resist external rotation of the tibia. It is taut in extension. Because it is extracapsular in part and well vascularised, isolated tears usually heal with bracing.
- Location
Medial side of the knee joint.
Anatomy
- Origin
Medial epicondyle of the femur.
- Insertion
Medial condyle and medial surface of the tibial shaft (below the joint line); deep fibres into the medial meniscus.
Function
- Resists valgus (abduction) stress at the knee
- Limits external rotation of the tibia
- Anchors the medial meniscus
Clinical significance
MCL sprain
Commonest knee ligament injury — a blow to the lateral knee (valgus). Medial joint-line pain and laxity on valgus stress at 30° flexion (graded I–III). Part of the unhappy triad with the ACL and medial meniscus.
Test yourself
A footballer is struck on the lateral side of the knee while his foot is planted. Which combination makes up the classic "unhappy triad"?
- PCL, fibular collateral ligament and lateral meniscus
- ACL, PCL and patellar ligament
- Tibial collateral ligament, patella and lateral meniscus
- ACL, tibial collateral ligament and medial meniscus
Answer: ACL, tibial collateral ligament and medial meniscus
A valgus blow with rotation tears the tibial collateral (MCL) ligament, the ACL and the medial meniscus — the medial meniscus being attached to the deep MCL. (MRI studies show the lateral meniscus is often injured in acute ACL tears, but the classic triad remains a high-yield exam answer.)
Why is the medial meniscus injured more often than the lateral meniscus?
- It is attached to the tibial collateral ligament and joint capsule, making it less mobile
- It is avascular throughout
- It is attached to the popliteus tendon, which tears it during flexion
- It is thinner and O-shaped
Answer: It is attached to the tibial collateral ligament and joint capsule, making it less mobile
The C-shaped medial meniscus is firmly attached to the capsule and the deep fibres of the tibial collateral ligament, so it cannot move out of the way of the femoral condyle during twisting. The lateral meniscus is more mobile, being separated from the fibular collateral ligament by the popliteus tendon.
Compiled from standard anatomy and physiology references — see the Skeletal System sources. For education only; not medical advice.