Muscles In The Knee

By Josh Martin, ATC

Muscles In The Knee

muscles in the knee

Simplified anatomy of the human knee.

The knee is a simple but complex joint in the human body. The knee is comprised of both static and dynamic stabilizers that work together to stabilize the knee. Static stabilizers are non-contractile and consist of structures such as ligaments, capsules, and menisci. Dynamic stabilizers on the other hand are contractile and consist of structures such as muscle and tendons.

How do dynamic stabilizers work?

Dynamic stabilizers are muscles that cross a joint line that are responsible for co-contracting during movement to provide support to the joint. These Dynamic stabilizers can work isometrically or isotonically based on the movement/ exercise being preformed. An Isometric contraction is a type of muscle contraction that requires little to no movement.  An isotonic contraction is a type of muscle contraction that requires concentric and eccentric movements.  A concentric contraction is a type of muscle contraction which causes the muscle belly to shorten during a movement. An eccentric contraction is a type of contraction which causes the muscle belly to lengthen during a movement.

What are the Dynamic Stabilizers of the Knee?

Dynamic stabilization of the knee occurs anytime the knee is in motion. These muscles provide support by contracting back in fourth to maintain proper anatomical alignment of the musculoskeletal system. If damage occurs to one or more of the dynamic stabilizers within the knee, it can impede functions such as strength, range of motion, balance, and postural alignment.


                  The knee is surrounded by multiple muscles that support the actions of knee stabilization, flexion, and extension. The quadriceps are made up of four main muscles they are the; Vastus Lateralis, Vastus Intermediacies, Vastus Medialis, and Rectus Femoris. These four muscles are located on the “anterior” front side of the leg and aid in knee extension. The hamstrings are comprised of three main muscles they are the; Biceps Femoris, Semitendonosus, and Semimembranosus. These muscles are located on the “posterior” backside of the leg and aid in knee flexion.   In addition to the Hamstrings, there are secondary muscles that help assist during knee flexion, they are the; Sartorius, Popliteus, Gracilis, and the Gastrocnemius. These muscles are located on the posterior aspect of the leg as well.



Muscular Injury Types

                  In general, there are two types of muscular injuries that occur around the knee.  The most common muscular injury would be a muscular contusion.  A contusion is caused by a direct blow/ impact to a muscle resulting in damage to soft tissues structures. This injury typically results with swelling and bruising around the affected area. The next most common muscular injury would be a muscular strain. A strain is a partial or complete tear within a muscle. These are commonly observed when the muscular structures are stretched/ pushed beyond there normal limits.  Muscular strains are graded on a scale from one to three all based on the severity of the strain.

A grade one strain occurs when five percent or less of the muscular fibers/ structures are damaged during the injury. This usually results in mild pain and bruising with minimal loss of strength and function. A grade two strain occurs when there is more extensive damage to the muscle fibers. This typically results in pain, bruising, loss of strength, and loss of range of motion. Lastly, a grade three strain results in complete rupture of the muscle or tendon.  Patients with a grade three strain will typically complain of pain, swelling, bruising, and complete loss of function.

Muscular injury Treatment

                  Muscle contusions and strains around the knee require separate methods of treatment depending on the severity of the injury. Typically, contusions and grade one strains require the same treatment method. These are commonly handled by using the “RICE” method. RICE stands for rest, ice, compression, and elevation. Anti-inflammatory medication may be used to help prevent/reduce swelling and pain over the affected area. Muscular strains that are greater than a grade one will require a more in-depth recovery process.

Grade two muscular strains typically have a longer recovery time frame and can sometimes be aided with a “PRP” platelet-rich-plasma injection to speed up the recovery process. Following the initial treatment method, physical therapy should be initiated to regain strength and function of the affected area. Grade three muscular strains/complete ruptures often require surgical intervention due to the severity of the injury. Further, doctors will evaluate each case to determine if surgical intervention will be necessary. Weather or not surgical intervention will be necessary; a brace will be required to be worn for a short period of time to allow the muscle to recover enough before starting physical therapy.

Where do I get Help?

No matter what the cause of your injury maybe, remember JOI is always here to help. Jacksonville Orthopeadic Institute offers up to date clinical practices to help aid in your recovery.


JOI Fracture and Injury Care

JOI Physicians are currently offering ASAP fracture and injury care. Further, this is a new option for patients who would like to avoid the emergency room if they have suffered a fracture or soft tissue injury. To learn more about this service, read this article about fracture and injury care. Make an appointment by calling (904)JOI-2000.

Please do not hesitate to call JOI for your medical needs. Further, we have surgeons that can help diagnosis your tear and therapy staff waiting to help rehab you back to full health! Please call JOI-2000 or click the banner below to schedule with one of our specialists.


Book An Appointment with a JOI Physician.

Image of Book An Appointment with a JOI Physician Button.


Written by: Josh Martin, ATC

Skip to content