Knee Mystery

author : AMSSM

comments : 1

This article covers a variety of injuries that can lead to knee pain.

Member Question

I need some help. Five weeks to the day I went out on a run and about a hour into it I had pain in the back and the side of my left knee, with radiating pain going down the inside of the calf and front of the knee.  I stopped and walked home.  Thinking it was some kind of pulled muscle I proceded with ice treatment for two weeks and did not run. I could tell by going up stairs and other activities that it was not fully healed. The main feeling and symptoms are weakness behind the knee and to the inside back of the knee. The weird part is I get stinging/heat achey pains on the inside of my thigh and calf. 

With the feeling of weakness and discomfort I haven't run at all. I'm still icing it but its not having any effect. The front of the knee does not hurt anymore.

I was leaning towards tendonitis but surely it should be showing signs of recovery?

Answer from Kelly Chain, MD and Chris Koutures, MD, FAAP
Member AMSSM

Sorry to hear of your injury and training limitations.

For an athletic person who does daily repetitive training, overuse injuries are the most common, such as tendonopathies or a muscular strain. These injuries are caused by the repetitive mechanical stress. The three sets of muscle/tendon groups in the back of the knee that are susceptible to injury are the hamstrings (posterior thigh muscles), gastrocnemius (posterior calf muscles), and popliteus tendon/muscle complex. The hamstring is responsible for knee bending and hip straightening and injuries can cause an achy sensation in the back and inner portions of the knee. This can be caused by sprinting activities, improper running techniques, poor warmups, or poor flexibility.

Gastrocnemius injury results in pain with knee bending against resistance and calf raises. This muscle is susceptible to injury because of it’s superficial location and because it crosses both the knee and ankle joints- thus it is often injured when the knee is in a fully extended position and the ankle is dorsiflexed (toes pointing upwards) which places the muscle at maximum stretch. The gastrocnemius pulls the heel upward and extends the foot downward and delivers propelling force needed in running and jumping.

Popliteus injuries can be due to a direct muscle stretch or when overused to maintain knee posterior and lateral stability. The popliteus helps maintain rotational stability of the knee and participates and assists in knee flexion. A popliteus strain is associated with pain in the back of the knee when weight bearing and with the knee bent 15-30 degrees. Injury can be due to a fall with the knee in an extended position or due to chronic overuse with poor running biomechanics or with poor training progression.

Meniscal pathology, either an acute or degenerative tear, can be another cause of posterior knee pain. Menisci are C-shaped shock absorbing pads on the inside and outside of the knee that help evenly distribute the weight of the body and diminish the amount of stress on both the cartilage and bones in the knee. The posterior horn (back of the meniscus) is the most common area for degenerative meniscus tears due to repetitive use and continuous shock absorption during activity. Eventually the meniscal tissue simply wears out. Injuries to the posterior horn of the medial or lateral meniscus often give more vague symptoms of posterior knee pain, commonly seen in runners. In addition to pain, meniscal tears can also give the sensation of knee catching or popping during activity. An acute meniscus tear can occur after a forceful blow or twisting, such as a sudden pivot during sporting activities. 

Another possibility is injury to one of the four main ligaments supporting the knee. The most common ligament injury associated with posterior knee pain is a Posterior Cruciate Ligament (PCL) injury which usually occurs only with high impact injuries, such as hitting the knee against the dashboard in a car accident, and is not likely a repetitive movement injury. Anterior Cruciate Ligament (ACL) injuries are more common than PCL injuries, and can rarely cause posterior knee pain as well. Frequently these are associated with a traumatic event such as a direct hit to the knee while the foot is planted. Non-contact injuries to the ACL can also occur and are usually secondary to landing from a jump, cutting or decelerating during an activity. In these injuries the knee is often unstable and it is uncomfortable to bear weight. A sprain of the inside of the joint capsule and the Medial Collateral Ligament is possible, but again this is most often due to a forceful trauma and not usually due to repetitive overuse.

Treatment options depend on the type of injury sustained. For tendonopathies or muscular strains, rest, ice, compression, non-steroidal anti-inflammatory medications (if needed for initial pain relief), and gradual return to activity is the best early strategy. To prevent re-injuries a proper warm-up and stretching after activity is important. If a meniscus tear or ligamentous injury is the cause of the pain more extensive interventions may be needed. If you are experiencing knee joint instability, catching, or persistent/worsening pain, it is always best to see a sports medicine physician to make sure the injury is not one that would require further medical management.

Hope that you recover quickly and can return to your normal physical activity as soon as possible.

Kelly Chain, MD, Pediatric Resident, Children's Hospital of Orange County/UC Irvine Pediatric Residency

Chris Koutures, MD, FAAP

Pediatrics and Sports Medicine

Anaheim Hills, CA

Medical Team Physician, Cal State Fullerton and USA National Volleyball Teams

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date: January 25, 2013