This article is part of our Injury Analysis series.
Jerick McKinnon and Matt Breida
The 49ers starting running back Jerick McKinnon made an early exit from practice on Sunday with what appeared to be a knee injury. McKinnon was seen grabbing the back of his right knee and would later undergo a MRI on the area. The medical imaging revealed a low-grade calf strain that will keep him sidelined for at least a week.
The results of the MRI may surprise people that don't normally associate the calf muscle complex with the knee. However, the calf is a two-joint muscle, meaning it's active in two different areas. Most people know the calf attaches to the heel via the Achilles' tendon, but they tend to overlook that it originates above the knee joint. The gastrocnemius and the soleus, the two muscles that comprise the calf, begin at the end of the femur and the tibia. As a result, the muscle group is able to play a role in knee flexion as well as plantarflexion of the ankle.
This positioning and dynamic role can prove detrimental when an injury occurs. A strained calf can cause limitations at both joints, a big setback for a position like running back that depends on explosive movement. Even worse, a strained calf can have a crossover effect on the muscles of the hamstrings. The aforementioned starting point of the calf sits in close proximity to the insertion site of the hamstrings. This location allows the two groups to work together to bend the knee. Unfortunately,
Jerick McKinnon and Matt Breida
The 49ers starting running back Jerick McKinnon made an early exit from practice on Sunday with what appeared to be a knee injury. McKinnon was seen grabbing the back of his right knee and would later undergo a MRI on the area. The medical imaging revealed a low-grade calf strain that will keep him sidelined for at least a week.
The results of the MRI may surprise people that don't normally associate the calf muscle complex with the knee. However, the calf is a two-joint muscle, meaning it's active in two different areas. Most people know the calf attaches to the heel via the Achilles' tendon, but they tend to overlook that it originates above the knee joint. The gastrocnemius and the soleus, the two muscles that comprise the calf, begin at the end of the femur and the tibia. As a result, the muscle group is able to play a role in knee flexion as well as plantarflexion of the ankle.
This positioning and dynamic role can prove detrimental when an injury occurs. A strained calf can cause limitations at both joints, a big setback for a position like running back that depends on explosive movement. Even worse, a strained calf can have a crossover effect on the muscles of the hamstrings. The aforementioned starting point of the calf sits in close proximity to the insertion site of the hamstrings. This location allows the two groups to work together to bend the knee. Unfortunately, this co-dependence leaves the healthy muscle group vulnerable following an injury to the other complex.
As a result, it's worth elevating McKinnon's injury risk for the immediate future. San Francisco is wisely slow-playing the situation, but those already invested McKinnon may want to handcuff him with one of the other Niners running backs. Breida would be the most logical candidate if not for an injury of his own. The backup running back suffered a shoulder injury in the team's preseason win over the Cowboys. The injury was described as a separated shoulder, providing insight to the area of the joint damaged.
The shoulder is made up of multiple joints and articulations, though most people generally think of the glenohumeral joint (ball-and-socket) as the shoulder. However, the nearby acromioclavicular (AC) joint plays an important part of shoulder motion. The AC joint is located where the collarbone meets the shoulder blade at a bony process known as the acromion. The joint acts a strut for the arm and is fortified by multiple ligaments. When the AC joint is sprained and ligament damaged is accrued, it's often referred to as a "shoulder separation." AC sprains are graded based on the amount of damage and the involved structures. Based on the reported information from Breida's MRI, it sounds like he suffered a low-grade sprain. The team will hold him out for the remainder of the preseason, preventing him from earning a bigger role in the Niners offense. Now, Joe Williams, Jeremy McNichols and Raheem Mostert will all fight for the backup running back job. Keep an eye on how they are utilized in the weeks leading up to Week 1 to determine which one earns the reps.
Turf Burns
Saquon Barkley: The highly touted rookie running back was seen wearing a wrap on his left leg during Monday's practice. Head coach Pat Shurmur seemed unconcerned about Barkley's status, but expect him to undergo a more thorough examine and evaluation in the near future. Keep your fingers crossed that it's simply a minor issue and that Barkley will miss minimal time.
Antonio Brown: The top-rated fantasy wide receiver returned to practice over the weekend after missing 10 days with a quadriceps injury. Brown took part in a majority of the drills and appeared unencumbered by the injury. Continue to draft him with confidence.
Isaiah Crowell: The New York Jets running back scored a touchdown in his first action with his new team but suffered a head injury on the play. He was later diagnosed with a concussion. Crowell well need to complete the league's mandated concussion protocol but should be fine in time for the start of the season.
Derrius Guice: The rookie running back will see his professional debut pushed back a year after he suffered a torn anterior cruciate ligament (ACL) in Washington's first preseason game. The timing of the injury is unfortunate for 2018 but occurred early enough that it shouldn't carry over into 2019. Now the team will be forced to use the running back by committee approach they employed last year, rotating between Rob Kelley, Samaje Perine and Chris Thompson.
Aaron Jones: Jones has become somewhat of a forgotten man in Green Bay due to his looming suspension and a hamstring injury. However, Jones returned to practice over the weekend and could be a draft day bargain if he manages to remain healthy for the remainder of the preseason. He's capable of reeling off big plays and a stretch of sustained health should earn him reps when he returns in Week 3.
George Kittle: Like his teammate Breida, Kittle is out with a low-grade shoulder separation. He's expected to sit for the remainder of the preseason nursing the AC sprain. Fortunately, the team is confident he will ready for Week 1, and Kittle is worth consideration in a suddenly shallow tight end field.
Carson Wentz and Nick Foles: Philadelphia's quarterbacks were limited for most of last week. Wentz continues to work his way back from a torn ACL and additional knee damage. He has been an active participant in 7-on-7 drills but has not taken part in 11-on-11 activities. Fortunately, the team is happy with his arm strength and footwork as he continues to progress. However, the Eagles remain noncommittal on a timeline for Wentz, leading to their conservative approach with Foles. Foles has been bothered by spasms in his shoulder and neck, specifically his trapezius. However, the issue isn't considered a major injury, and Foles was back in action over the weekend. The two remain linked for fantasy purposes.
