MCL: Refixate, reconstruct, or leave it alone?

The clinical foundation

To approach MCL injuries rationally, it’s essential to understand the anatomy and function of the medial stabilizing structures. The MCL complex is not just a single band but consists of the superficial MCL (sMCL), deep MCL (dMCL), and the posterior oblique ligament (POL). The sMCL is the primary restraint to valgus stress at both 0° and 30° of flexion, but the POL and dMCL contribute significantly, especially when the knee is fully extended. The POL also helps resist posteromedial rotational and posterior tibial forces. Most recently, anteromedial MCL structures have been identified to limit anteromedial rotational instabilities as well.

This anatomy underpins the clinical exam: slight valgus instability in slight flexion but not extension indicates a partial sMCL injury, while higher grade instability in both extension and flexion signals a more severe, complex injury involving the POL and dMCL as well. In addition, increased external rotation in the 90° flexed may indicate anteromedial rotational instability.

The first decision: partial or complete?

The first, and perhaps most important, decision in MCL management is determining the completeness of the injury. This is best done with a careful, comparative valgus stress test in both full extension and about 30 degrees of knee flexion.

Partial MCL injuries that open only mildly (1° degree) in slight flexion and are stable in extension are overwhelmingly suitable for non-operative treatment. Functional bracing, permissive weight bearing, early controlled mobilization, and a return to sports protocol yield excellent results. The ability of the sMCL to heal is well established, and there is little benefit to surgical intervention if the deep structures and the POL are intact.

Complete MCL complex disruptions reveal themselves with higher degree valgus gapping in both flexion and full extension. Here, the risk of chronic instability, ACL graft overload (if concomitant), and poor outcomes rises sharply. These injuries demand further scrutiny and often a surgical solution.

The second decision: Where is the lesion?

Medial collateral ligament (MCL) injuries can be classified by the location of the tear, with each pattern presenting distinct challenges and treatment considerations. Understanding the differences between femoral-sided, midsubstance, and tibial-sided lesions is essential for optimal management and surgical decision-making.

Femoral-sided tears

Femoral-sided MCL injuries are among the most frequent patterns, often presenting as avulsions from the medial femoral epicondyle. These can be subtle on MRI and missed if not specifically sought.

Acute femoral-sided injuries, particularly those encountered during early surgery (e.g., at the time of ACL reconstruction), are excellent candidates for anchor-based refixation. The tissue quality is usually good, and the proximity of the tear to bone facilitates healing. This approach preserves the native ligament, maintains proprioception, and avoids the morbidity of graft harvest.

Chronic femoral-sided injuries or those with attenuated, poor-quality tissue, however, are less likely to succeed with primary repair. Here, anatomic reconstruction with autograft or allograft is preferred.

Either fluoroscopy or intraoperative isometry testing are invaluable for accurate anchor placement: the isometric point on the femur must be restored, or the risk of post-op stiffness or residual laxity rises.

Midsubstance tears

Midsubstance MCL injuries, where the ligament is torn away from itself (rather than at its bony attachments), are less common but present a unique challenge. A key distinction is whether the torn ends are well apposed or displaced.

Non-displaced midsubstance tears can often be managed non-operatively, as the ligament’s natural healing potential is good if the ends are in contact.

Displaced midsubstance tears are unlikely to heal well without intervention. Direct suture repair offers the advantage of supporting intrinsic healing of a biomechanically complex structure. In chronic cases of medial, reconstruction of the biomechanical unstable structures is mandatory in order to address the correct direction of instability.

Tibial-sided (stener-like) lesions

Perhaps the most controversial and crucial group are the tibial-sided or so-called "Stener-like" MCL lesions. In these cases, the distal MCL is avulsed from the tibia and may become trapped superficial to the pes anserinus or hamstring tendons—analogous to the classic Stener lesion in the thumb UCL.

These injuries have a very poor prognosis with non-operative management. The interposed tissue prevents the MCL from healing back to its anatomic bed, and persistent valgus instability is the rule, not the exception.

The consensus among experts is clear: these lesions should be repaired acutely, with anchor-based refixation and, ideally, suture augmentation. Missing this injury can doom the knee to chronic instability and failed ACL grafts.

Combined ACL–MCL injuries: the algorithm evolves

The management of MCL injuries becomes even more nuanced when paired with ACL ruptures—a scenario frequently seen in contact sports. In these cases, the correct sequence and method of treatment are critical to success.

Partial MCL + ACL rupture

If the MCL tear is partial and stable in full extension, bracing is recommended. The ACL reconstruction is delayed for 4–6 weeks, allowing the MCL to heal and reducing the risk of post-op stiffness or failure.

Complete MCL + ACL rupture

If the MCL is completely torn, especially with a tibial-sided or displaced femoral injury, both ligaments should be addressed surgically in one session. Failure to do so can result in excessive medial laxity, overloading and stretching the new ACL graft.

Graft choice: Don’t rob Peter to pay Paul

A crucial technical consideration is the graft selection. The hamstrings (semitendinosus and gracilis) are secondary stabilizers of the medial knee, especially in valgus and rotational stress. If the MCL is being reconstructed, preserving the ipsilateral hamstrings is advantageous, as their loss further weakens medial stability. Thus:

• If reconstructing MCL: Use contralateral hamstrings or ipsilateral quadriceps tendon for ACL reconstruction.
• If only refixating MCL: Ipsilateral semitendinosus may still be used, but many prefer quadriceps tendon, especially in high-demand athletes.

I usually favor the quadriceps tendon for ACLs in combined injuries, both to protect the medial side and to avoid further hamstring morbidity.

Technical pearls, pitfalls, and postoperative care

Optimal outcomes in MCL repair depend on careful attention to anchor placement, identification and management of associated ligament injuries like the POL or anteromedially capsule ruptures, and a comprehensive approach to augmentation and bracing during rehabilitation.

Anchor-Based Refixation

Success in primary MCL repair hinges on restoring the native ligament’s length and isometry. Use intraoperative fluoroscopy to place femoral anchors at the anatomic origin. Non-anatomic placement is a leading cause of postoperative stiffness or residual laxity.

POL: the hidden culprit in extension instability

If valgus instability persists in full extension after MCL repair, suspect injury to the posterior oblique ligament (POL). Addressing the POL with a separate anchor or suture repair is often necessary, especially in higher-grade injuries.

Common mistakes

Several pitfalls consistently trip up even experienced surgeons:

1. Ignoring full-extension instability: Always assess both in flexion and extension. Extension instability almost always means the POL is involved and must be addressed.
2. Non-anatomic anchor placement: Take time with fluoroscopy and clinical assessment to ensure you are restoring normal isometry—especially on the femoral side.
3. Waiting on Stener-like lesions: These simply do not heal reliably without surgery. Early repair is the rule.
4. Harvesting the ipsilateral hamstrings when reconstructing the MCL: This weakens secondary restraints and can set up residual instability.

Putting it all together: the algorithm in action

Let’s consider a practical example: A 24-year-old soccer player sustains a valgus-external rotation injury. She presents with valgus instability in both flexion and extension, and MRI reveals a tibial-sided MCL avulsion (“Stener-like”) and a complete ACL rupture. The algorithm would recommend:

• Early surgical intervention for both ACL and MCL.
• Anchor-based refixation of the tibial MCL.
• ACL reconstruction with quadriceps tendon (preserving hamstrings for medial stability).
• Intraoperative fluoroscopy to ensure anatomic anchor placement.
• Postoperative bracing and staged rehabilitation protocol.

In contrast, an older recreational athlete with a partial MCL tear (stable in extension and only mildly in flexion) and intact ACL would be managed non-operatively, with bracing and physical therapy.

Imaging and surgical planning: The role of MRI and fluoroscopy

Accurate diagnosis and planning are essential. MRI is invaluable for pinpointing lesion location (femoral, midsubstance, tibial), identifying tissue interposition in Stener-like lesions, and assessing associated injuries (meniscal, POL). Intraoperative fluoroscopy, especially during anchor placement, ensures restoration of normal ligament length and tension.

Pragmatism, not dogma

The management of MCL injuries is not a one-size-fits-all endeavor. By anchoring your decisions in the location and grade of the lesion, the presence of concomitant injuries, and the nuances of tissue quality and patient demand, you can tailor treatment for each case. This stepwise, pragmatic algorithm—embracing primary repair, anatomic reconstruction, or non-operative management as the situation warrants—ensures optimal outcomes and avoids the common traps that can sabotage even the best intentions.

MCL injuries demand respect, but with a thoughtful, evidence-based approach, most patients can look forward to restored stability, function, and return to play.