29 August 2014

Further Discussion of Manny Machado and the Patellofemoral Joint

Wednesday found Orioles third baseman Manny Machado again under the knife, this time to repair a partial tear of his right medial patellofemoral ligament (MPFL); it was performed by Dr. Neal ElAttrache, the same surgeon who repaired his left knee last season. By all reports, the procedure went well and Machado should be able to start the rehabilitation process without any delays. However, news of yet another season ended prematurely by knee injuries for Machado has not only brought skepticism to the rest of season fortunes for the Orioles, but also to the young infielder's chances of a long and productive career. With a 2014 already shortened by an extended rehabilitation from the left MPFL rupture and patellar subluxation suffered in September of 2013 as well as the more recent right knee sprain suffered that evolved into Wednesday's surgery, the revelation of the left MPFL tear casts doubt as to whether he can sustain the physical rigors of the typical MLB season; these injuries also amplify the scuttlebutt on moving Machado to his natural (and more physically demanding) position of shortstop.

For the moment, let's set aside the gloom surrounding the coming years for Machado on the field and take a focused look at the anatomy involved with his knee problems and the surgical procedure he has undergone with Dr. ElAttrache, with the hope that with a better understanding of the medical intricacies of the situation, the doubts and anxiety surrounding Machado's future can be alleviated or at least put into better perspective.

For better or worse, much of the anatomy of the knee joint and the MPFL in particular has been discussed here at Camden Depot; you can find previous articles here and here. Briefly, the MPFL is a ligament that attaches at the femur and patella and helps resist lateral migration of patella, providing a significant amount of the restraining force against the patella dislocating. With the anatomy and mechanisms innate to the MPFL already discussed, let's now shift focus to another crucial piece to the knee joint puzzle and to Machado's health—the anatomy of the trochlea (also called trochlear groove) of the femur and its relationship with the MPFL.

Collectively, this region of interest is called the patellofemoral joint and consists of the patella and its articulation with the trochlea, with the primary role of the patella increasing the mechanical advantage of the quadriceps muscles of the thigh. The stability of this joint is maintained by a complex interaction between soft tissues and bony structures. Stabilizers of the joint are often divided into three groups: active soft tissue stabilizers (the quadriceps), passive soft tissue stabilizers (ligaments) and static stabilizers (the bony anatomy between the patella and trochlea).

With respect to articulations, the patella is covered in cartilage posteriorly that allows for the bone to glide seamlessly along the femur via the trochlea, with seven facets of the patella coming into contact with the femur as the knee flexes and extends. Normal activities typically find five of these seven surface in contact with the femur. The alignment and positioning of the patella is also important and assists in determining the biomechanics of the knee and how the lower legs 'hang', forming the Q-angle, which is an important aspect of the geometry of the knee. The average Q-angle is 14 degrees for males, with anything over 17 degrees considered excessive and called genu valgum—knock-kneed. Smaller Q-angles are thus considered genu varum, or bow-leggedness. Excessive Q-angles can predispose a person to patellar subluxations, such as those suffered by Machado.

Also potentially complicit in patellofemoral instability is the trochlea itself. In the condition trochlear dysplasia, the trochlea is not properly shaped and the patella does not have the normal bony constraints to provide stability. In essence, the trochlear groove is 'flat' and does not exhibit its usual concave shape, giving the articular facets of the patella less surface area to touch, causing a less stable articulation between the two bones. This leads to reliance upon on the MPFL and quadriceps to hold the patella in place, creating a higher than usual propensity for MPFL ruptures and patellar dislocations, due to the decreased strength of the joint. Along with trochlear dysplasia, conditions such as patella alta (a small knee cap) and lateralization of the tibial tuberosity can also affect joint strength. Ligament laxities, such as those seen in Marfan syndrome and Ehlers-Danlos syndrome can also provide patellofemoral instabilities, but are not frequently seen in the older athletic population.

Anatomy of the trochlea and patella. Taken from Practical Orthopaedic Sports Medicine & Arthroscopy 1st Edition, http://www.msdlatinamerica.com
Surgically, both the MPFL repair or reconstruction is a fairly straightforward procedure, with both lending much of the success to the less invasive, arthroscopic approaches that can now be performed. For repairs, tears of the ligament and other soft tissues are typically sutured, often with suture anchors placed in the femur for additional stability and strength, with patellar mobility assessed once sutures and anchors are placed. For a reconstruction, a graft, which is what Machado had previously performed on his other knee, typically the tendon of the semitendinosus muscle is harvested, with tunnels drilled into both the patella and femur for placement of the graft. Passage of the graft and fixation with sutures is also performed, with the native MPFL sutured to the graft and patellar mobility assessed before closure of incisions. It also appears that another procedure on top of either the repair or reconstruction (which is the more likely procedure to have been performed Wednesday) was also undertaken; while no confirmation of the procedure has been found, a common procedure that is often pursued along with the MPFL procedure is a trochleoplasty, which is performed to reshape the trochlear groove, allowing for increased patellofemoral stability.

At the end of all of these procedures, the future still remains slightly fuzzy for Machado. While these operations are necessary and will definitely allow him to return to action for next year, the question remains as to whether he will be the player he was prior to the surgeries. One study in particular looked at outcomes in athletes after MPFL reconstruction found that 100% returned to sports after MPFL reconstruction, 53% returned at equal or higher levels of performance, with 47% returning, but at lower levels of performance. Along with these subjective assessments of return to performance provided by the athletes, knee function was tested using a number of assessments that measured range of motion and pain, with postoperative improvements in these scores predominantly seen. However, there are a couple of caveats to these results, despite their somewhat encouraging tone. First, the athletes themselves were self-evaluating their levels of performance upon return to competition, so biases abound; no sport-specific statistics were used to objectively measure performance returns. Also, the authors included the caveat that these results were found in patients without severe trochlear dysplasia, which is something that could also potentially be ailing Machado.

Overall, youth is on Machado's side, as is the timing of the most recent procedure; the quicker the knee is repaired post injury, the better, and of course, the younger the patient, the more hopeful the medical staff are that a quick, complication-free recovery and rehabilitation will be seen. Using 2014 as a template for Machado's possible return in terms of performance next season, Orioles fans should be confident that his knee woes will be finally nipped in the bud, with his hitting less potentially affected postoperatively than his fielding. For his prowess with the glove, things are a little less certain, with the potential for a deterioration in Machado's lateral quickness a real possibility, especially considering both of his MPFL's are reconstructed. That being said, the future remains promising for Machado remaining in the upper echelon of young baseball talents despite his recent run of knee injuries.


Hamill, J., & Knutzen, K. (2009). Biomechanical basis of human movement. Philadelphia: Wolters Kluwer Health/Lippincott Williams and Wilkins.

Miller, M. (2011). Operative techniques in sports medicine surgery. Philadelphia: Wolters Kluwer Health/Lippincott Williams and Wilkins. 


Anonymous said...

As a medical student and Os fan, this is exactly what I needed to read today. Thanks for an excellent explanation.

Stuart Wallace said...

I appreciate the kind words, Anon! Fingers crossed this is the end of the knee woes for Machado...