The knee depends on four primary ligaments for stability, and injuries to any of these, from a partial sprain to a complete tear, can significantly limit athletic performance and daily function. While ACL injuries attract the most attention, the PCL, MCL, and LCL are equally important structures whose injuries require careful assessment and management.
What is Knee Ligament Injuries?
The four main knee ligaments are the anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), medial collateral ligament (MCL), and lateral collateral ligament (LCL). Each provides stability in a specific direction and is tested by specific clinical manoeuvres.
The PCL is the strongest ligament in the knee and is injured less frequently than the ACL, most commonly in dashboard injuries or direct blows to the front of the tibia. The MCL is the most commonly sprained knee ligament and is injured by valgus force applied to the knee. The LCL is less frequently injured in isolation and is most vulnerable to varus stress.
Types of Knee Ligament Injuries
Causes
A valgus force applied to the knee during a tackle or collision in football, kabaddi, rugby, or basketball is the primary mechanism of MCL injury. The same valgus force with greater energy can simultaneously injure the ACL, producing a combined ligament injury.Non-contact deceleration, sudden direction changes, and pivoting movements in sport are the most common cause of isolated ACL tears, particularly in football, basketball, cricket, and kabaddi. The mechanism typically involves the foot planted on the ground while the body rotates over it.
Dashboard injuries in road traffic accidents, where the bent knee is driven posteriorly by the dashboard on impact, are the classic mechanism of PCL tears. Falls onto a flexed knee with the foot plantar-flexed produce the same posterior force through the tibia. A direct varus force or blow to the inner aspect of the knee stretches and tears the LCL and posterolateral corner structures. This is less common than medial-sided injuries and often occurs in high-energy trauma.
High-energy sporting collisions, road traffic accidents, and falls from significant height are the typical mechanisms of multi-ligament knee injuries, where the forces involved are sufficient to dislocate the knee joint itself and disrupt multiple stabilising structures simultaneously.
- A pop or tearing sensation at the time of injury, most commonly associated with ACL tears and significant multi-ligament injuries
- Rapid swelling of the entire knee developing within hours of injury, indicating a haemarthrosis from ligament rupture
- A feeling that the knee is unstable or giving way, particularly during cutting, pivoting, or direction changes
- Pain localised to the medial or lateral joint line depending on which ligament is injured
- Difficulty bearing full weight or walking normally in the acute period following injury
- In PCL injuries: a sensation of the knee sinking backwards when descending stairs or decelerating, caused by posterior tibial subluxation
Diagnosis
Clinical examination assesses the integrity of each ligament using specific stress tests performed systematically. The Lachman test and anterior drawer test assess ACL integrity, with the Lachman test being more sensitive in the acute setting. The posterior drawer test and posterior sag sign evaluate PCL integrity. The valgus stress test at both 0 and 30 degrees of knee flexion assesses the MCL, and the varus stress test at the same angles evaluates the LCL. The dial test and external rotation recurvatum test assess posterolateral corner instability, and the pivot shift test assesses combined ACL and rotational instability under anaesthesia.
Plain X-rays are performed in all cases to exclude bony avulsion fractures, which can accompany ligament tears at their tibial or femoral attachment points. A Segond fracture, a small lateral tibial avulsion, is pathognomonic of an ACL tear. MRI is the gold standard investigation for confirming the diagnosis, grading the severity of each ligament tear, and identifying all associated injuries including meniscal tears, articular cartilage damage, and bone bruising patterns that influence the surgical plan. In suspected multi-ligament injuries with any concern about vascular compromise, CT angiography of the popliteal artery is performed urgently before any other intervention.
Treatment
Non-Surgical Management (MCL, most isolated PCL)
Isolated MCL and most isolated PCL injuries, even complete grade III tears, can be successfully managed non-surgically with bracing and physiotherapy, as these ligaments have excellent healing capacity with proper immobilisation. Most patients make a full functional recovery.
Surgical Reconstruction (multi-ligament injuries, failed conservative treatment)
Multi-ligament knee injuries, such as combined ACL and MCL or ACL and PCL injuries, require surgical reconstruction. Dr. Kushalappa addresses multi-ligament injuries using tendon graft reconstructions, staged where appropriate, with the goal of restoring full knee stability and enabling return to sport.
Why Choose Dr. Kushalappa Subbiah in Bangalore?
Dr. Kushalappa Subbiah completed a Fellowship in Shoulder Surgery at the Sydney Shoulder Research Institute, where he trained in advanced arthroscopic shoulder procedures including labral repair and reconstruction. He holds the International Olympic Committee (IOC) Diploma in Sports Medicine, and has direct clinical experience managing shoulder injuries in Indian athletes across cricket, swimming, tennis, and contact sports. He is appointed as a Consultant Shoulder Surgeon at NH Hospital, Bangalore.