Video Analysis – Stephen Curry’s Grade II MCL injury

In his first game back from rehabilitating a lateral ankle sprain over a six game absence, Warriors two-time MVP point guard Stephen Curry sustained a grade II MCL injury to his left knee in a collision with teammate Javale Mcgee.

The video below depicting Curry’s mechanism of injury serves as a reference point throughout this blog.  Play it through a few times to paint a picture of the mechanics of his injury.

The contact from Javale creates a valgus moment (an increase in the angle of the inside of the knee) on Curry’s knee.  Take a look:

This type of contact valgus moment is not common. It more commonly occurs in non-contact injuries and is typically attributed to poor hip stability and/or poor jumping/landing/stepping biomechanics.

Regardless of the specific mechanism, this valgus moment stresses the medial structures of the knee – most commonly the medial collateral ligament (MCL).  

The Medial Collateral Ligament (MCL) originates on the medial aspect (inside edge) of the femur and inserts onto the medial tibia, crossing the knee joint. Here’s a picture:

Since the MCL is the primary restraint to valgus moments, it took on significant stress & was compromised. An MRI conducted the following morning of the injury revealed a grade II sprain of the left MCL.

Given the mechanism of injury, Warriors medical staff would have likely suspected the following diagnoses in the locker room:

  1. MCL strain/rupture
  2. ACL rupture
  3. Lateral meniscus tear

MRI’s are certainly the gold standard in sports injury diagnosis, but as they typically take 24-48 hours to conduct, the medical staff (as well as Steph) would have been eager to know what they were dealing with.

The following section discusses how the Warriors medical staff used manual special tests to confirm if Steph had, or didn’t have, the following differential diagnoses:

Differential Diagnoses

MCL Sprain

As discussed above, any injury where a valgus (knee going inward) moment occurs likely results in a disruption to the medial structures, namely the MCL. The following tests are used to either rule in or rule out the presence of MCL involvement: 

  1. Palpation of the MCL
    1. tenderness indicates a positive test
  2. Valgus stress test
    1. pain with valgus stress and/or
    2. laxity felt by the clinician (gapping of the tibia away from the femur) indicates a positive test.
    3. With a sensitivity of 86%, the valgus stress test is reliable at picking up the presence of an MCL strain.

As steph sustained a grade II MCL sprain, there was likely considerable laxity and pain with valgus stress testing.

On an interesting note, if Steph’s MCL were completely ruptured, the nerve endings would no longer send afferent (from the body region back to the brain) pain signals and thus Steph would experience no pain with valgus stress testing. Additionally, a grade III (full rupture) tear would result in absolutely no end feel when completing the valgus stress test because there are no structures left to restrict valgus movement.

ACL Rupture

The dreaded ACL rupture. The ACL is placed under most tension when:

  1. the tibia is internally rotated and
  2. the knee is in a valgus position and
  3. the hip is adducted (aka thigh is moving toward the midline)

Although commonly ruptured in non-contact injuries, the perfect recipe for disaster can strike if a player’s knee is forced into these positions by contact from another player – like in Steph’s case with Javale making contact with his knee. 

In Steph’s mechanism of injury, you can see he is knocked into a valgus moment (as we talked about above) AND he exhibits adduction at the hip with the thigh moving toward his midline. Here’s the moment of his injury again:

Steph Curry MCL Grade II

If Steph’s foot had been slightly more internally rotated, he might have sustained an ACL rupture, leaving him sidelined for 9-12 months.

ACL Testing

I suspect head trainer Chelsea Lane was praying to the God’s that there was no laxity when she was performing the following tests:

  1. Lachman’s Test

2. Anterior Drawer Test

As the ACL prevents anterior translation (forward movement) of the tibia on the femur, the feeling of the tibia moving forward on the femur would indicate a positive test. Both the Lachman’s and Anterior Drawer have a Sensitivity of ~0.85 and Specificity of ~0.91 (depending on which RCT you read).

Given Steph had no disruption to ACL testing, he would have displayed no laxity on these tests and therefore tested negative.

Lateral Meniscus Tear

The menisci – both lateral (outside) and medial (inside) are typically disrupted when a player twists on a foot that is firmly planted on the ground. The lateral (outer) meniscus in particular can succumb to disruption whenever the lateral compartment of the knee is compressed – such as during a valgus movement. These pictures will help illustrate the anatomy and compression:

 

 

 

 

 

 

 

In Steph’s injury, his knee was placed into a valgus position resulting in compression of the lateral compartment.  Therefore, damage to the lateral meniscus needed to be ruled in or out. 

The Warriors medical staff would have done the following to determine meniscus involvement:

  1. Joint line palpation (lateral joint line for lateral meniscus)
    1. Tenderness indicates a positive test
  2. McMurray’s Test
    1. the go-to test to rule in or out the presence of meniscus involvement
    2. pain in the lateral compartment upon wind-up or wind-down indicates a positive test

Steph likely had no tenderness on the lateral aspect of his knee and no pain on McMurray testing.

Prognosis

The good news for Steph is that there was no concomitant disruption to any other structures in his knee. The fact that there was no additional muscle strain, bone bruising, meniscal disruption or ligament/tendon injury, plays heavily in Steph’s favor. It allows for faster healing of the MCL, and allows both Steph and the medical staff to focus their attention on rehabilitating one structure – rather than two, three or four simultaneously.

Estimated guidelines on return to sport as per Brukner and Kahn’s Clinical Sports Medicine guidelines are as follows:

  • Grade I MCL Sprain                 Partial fiber disruption                   0-2 weeks
  • Grade II MCL Sprain                ~ 50% fiber disruption                    2-6 weeks
  • Grade III MCL Sprain               Full rupture                                      6-12 weeks

The Warriors have informed the media that they will re-examine Steph in 3 weeks. This does not, and likely will not, mean that Steph will come back in 3 weeks time.

I suspect they have chosen the 3 week mark to review Steph as this coincides with round 1 of the playoffs. Now before you get excited, Steve Kerr has himself said that “there is no way he’s playing the first round“. But we can always be hopeful right? Or maybe not if you’re a Jazz fan like myself.

Treatment and Management

Now that the objective manual testing and follow-up MRI have confirmed that Steph has a grade II MCL sprain with a 2-6 week timetable for return, let’s discuss immediate treatment and management.

  1. Steph will be immediately placed in a ROM restriction brace. This is because knee extension (straightening) ranges less than 30° and knee flexion (bending) ranges greater than 90° have been shown to increase the tension on the MCL. As Steph’s rehabilitation journey progresses, the medical staff will gradually open up the ROM brace to allow for greater ranges of flexion and extension.
  2. The stages of rehabilitation:

*This is a conservative rehabilitation protocol timeline based on the experience I have had treating and managing MCL sprains. If Steph doesn’t encounter any problems, he may breeze through this in 2 weeks.

The Takeaway for Stephen Curry’s  Grade II MCL Injury

With last night’s 119-79 loss to the Utah Jazz, the Golden State Warriors are now 4-6 without Curry. This speaks volumes on how integral Curry is to the Warriors system, even with 3 All-Stars on the court.

With his re-evaluation date soon approaching on April the 14th, I suspect the Warriors medical staff will maintain a conservative approach to Curry’s return and rest him for round one of the playoffs. With Quinn Cook performing well at the PG position, in unison with the efforts of All-Stars Durant, Thompson and Green, Curry is able to focus on his rehab and disregard any pressure about returning early for the team to make it out of the first round. This will give Curry the best possible chance at a healthy return for round two.

Steph relies heavily on his lateral agility when coming off screens to create space for the contested three or driving into the lane and performing circus tricks under the rim. Lateral agility and side stepping require significant restraint from the MCL, so it will be interesting to see how Curry performs upon his return. We may see that Curry stays near the perimeter and avoids the paint, especially as he works the rust off.

However, if his previous games when returning from injury are taken into consideration, Steph displays pure confidence in his ability to leave the three and finish under the rim, a trait that makes him one on of the most difficult players to defend in the league.

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