Today, my chiropractic health assistant and I are writing about a rare and often misdiagnosed condition associated with the knee joint and tissue structure surrounding the knee. There are various knee conditions such as Anterior Cruciate Ligament Strain/Sprains/Tears (ACL), Posterior Cruciate Ligament Strain/Sprains/Tears (PCL), Meniscus irritation, and Patellofemoral Arthralgia that get diagnosed correctly. However, at times, a simple strain/sprain/tear injury to the muscles at the back of the knee goes undetected.
Just the other day, a 30 year old runner came into the clinic complaining of posterior (back of the knee) pain. The knee pain started after he ran 5km over the weekend. The patient went to his medical doctor and his doctor indicated to rest and ice the knee. The medical doctor referred the patient to our chiropractic clinic for further physical investigation.
We tested the knee for any Anterior Cruciate Ligament (ACL), Posterior Cruciate Ligament (PCL), Medical/Lateral Collateral Ligament, and menisci damage. All the tests were negative. The patient explained that he felt the pain most when we touched the back area of the knee (mushy area) while in a flexed position. No baker cysts (small ball like structure that can be felt at the back of the knee) were felt. The patient also explained that he felt pain while we tested his knee flexion. We quickly understood the cause of his pain. This rare condition is called Popliteus Syndrome or Popliteus Strain.
The Popliteus knee muscle is responsible for internal rotation of the shin bone (tibia) as well as for unlocking the knee joint when bending the knee from a fully straightened position (extended position). The popliteus muscle originates from outside surface of the knee and goes on to attach to the back aspect of the inside area below the knee joint.
This muscle is often injured through acute injury (sport injuries, car accident or fall) or overuse.
Acute injuries to the popliteus occur after a significant force to the knee. They are common in road traffic accidents or falls where the knee is extended. Popliteus injuries may occur in association with other knee injuries occurring to the ACL, PCL, Meniscus and Collateral ligament. Thus, it is important to screen for this muscle injury at all times and especially in the presence of other knee injuries.
Overuse injuries to the popliteus muscle develop gradually and are most common in runners. They tend to be due to biomechanical issues (foot issues) and tight hamstring muscles, quadriceps and calf muscles. We explained this to our patient.
We went forward by treating the patients knee joint. We started with therapeutic ultrasound, laser therapy and electrotherapy to the posterior/back area of the knee. Following this, we proceeded with soft tissue therapy (15 minutes) to the popliteus and stretched the calfs, hamstrings and quadriceps. The patient returned the next day for a second treatment. After the second treatment, the patient explained that he was much better and did not experience any more locking/pain in the knee joint. The patient went back into training in a progressive fashion (1km added to each day without pain). We made sure that the patient followed proper warm up and stretching instructions in order to prevent the injury from reoccurring. Two weeks following the injury, the patient returned to explain that he ran 5km with no issues.
As one can see, it can be easy to ignore this muscle especially with the other knee areas/injuries/concerns that are often more common. It is critical to always evaluate all the soft tissues in the knee area (fascia, tendons, muscle, and ligament) in order to avoid missing this often under/misdiagnosed injury. If you have any feedback or comments, please write to us.
MEDICAL DISCLAIMER: The following information is my personal notes about this subject matter. It is intended for informational purposes only. Consult a health practitioner to help you diagnose and treat injuries of any kind.
Dr. Luciano Di Loreto, HBSc., DC
Chiropractor in Woodbridge, Ontario
The Locked Knee Syndrome
Over the last few years, I have worked on a variety of patients with knee problems. Contrary to the general perception, not all knee problems and conditions occur in the adult or elder population. In fact, some conditions occur more frequently in children and teenagers. Some of these younger patients present with laxity or a loose knee, while others present with locking in the knee. Regardless of age or type of knee concern, a thorough history and physical examination is extremely important to conduct if we are to rule in and rule out conditions. Today, I will dive into the intricacies of the typical locked knee patient. I will answer the following questions. What makes up a knee joint? What is a knee lock? What causes a knee to lock? What treatment options are available for a locked knee?
Anatomy of the Knee Joint
Let us learn about the anatomy of the knee joint. Our knee joint is made up of a variety of bones. You have the femur, tibia, and patella (kneecap). These bones together are involved in creating the knee joint and/or involved in knee function (mainly bending). In between the femur and tibia (see picture) there are two menisci. You have one meniscus located on the inside (medial meniscus) and one meniscus on the outside (lateral meniscus) of your knees. The menisci are made of tough cartilage that fits nicely between the bones. Surrounding the knee joint, you have layers of muscle. There are two groups of muscles at the knee. The four quadriceps muscles, on the front of the thigh work to straighten the knee from a bent position. The hamstring muscles, which run along the back of the thigh from the hip to just below the knee, help to bend the knee. You also have a number of ligaments that stabilize the knee joint. You have four ligaments that connect the femur to the tibia. The medical collateral ligament (MCL), lateral collateral ligament (LCL), anterior cruciate ligament (ACL), and posterior cruiciate ligament (PCL).
Let us talk more about the Menisci
The menisci are important because they distribute weight across the knee joint. If you lack menisci or a meniscus, weight would be unevenly distributed across the joint, leading to uneven force distribution and early arthritis of the knee joint. Another important function of the meniscus is to keep the knee joint stable. The menisci are crucial to the health of your knees!
Life as a Meniscus
The menisci are nourished by small blood vessels along the outer surfaces. They do not receive any nourishment in the inner areas. As a result, this becomes a problem when an injury occurs within the inner areas. Without a proper blood supply, essential nutrients cannot reach the inner injured menisci for healing to occur. Thus, the menisci do not heal properly in the inside areas.
What does this mean?
The menisci can be easily injured by the force of rotating the knee while bearing weight. A partial or total tear of the meniscus may occur when a person quickly twists or rotates the upper leg while the foot stays still. If the tear is tiny, the meniscus stays connected to the front and back of the knee; if the tear is large, the meniscus may be left hanging by a thread of cartilage. The seriousness of the tear depends on its location and extent. A patient with a menisci injury will most commonly experience knee pain, swelling, tenderness, popping or clicking and/or limited motion or locking of the knee.
Finally! Why does the knee lock?
Severe pain and/or locking may occur if a fragment of the meniscus catches between the femur and tibia within then knee joint. Pain may go away while the locking may continue to persist due to the fragment of torn meniscus floating around the knee joint.
Ok, my knee locks, now what?
When presenting with a suspected meniscus injury such as a meniscus tear, which may cause a locking of the knee joint, it is important to conduct x-rays and/or MRI to verify the extent of the injury. Remember, x-rays are conducted to visualize bone, while MRI’s are conducted to visualize soft tissue structures such as the meniscus. Visualizing a torn meniscus on MRI does not mean a specific treatment is required. Treatment depends on several factors.
Treatment Possibilities for a Meniscus Tear
Treatment of a meniscus tear or locked knee depends on several factors including: type of tear, response to conservative treatment and the activity level of the patient. Many menisci tears are treated non-surgically via pain control modalities (electrotherapy, ultrasound, laser therapy), soft tissue therapy, acupuncture and rehabilitation. In practice, interferential current and acupuncture helps to reduce pain. Furthermore, laser therapy and ultrasound therapy can assist in healing of some areas of the meniscus and the surrounding soft tissues. Soft tissue therapy can help with loosening tight quadriceps and hamstring muscles. Last, but not least, it is important to commence a rehabilitation and exercise program to strengthen muscles. These treatment methods are effective; however, everyone is unique and will respond differently to these conservative treatments.
If conservative non-surgical treatment fails to alleviate pain and a patient continues to experience mechanical knee symptoms such as locking, inability to straighten and clicking/popping noises – he/she may consider surgical options.
When surgery is necessary, a surgeon may discuss the following options to help improve mechanical symptoms. Either remove the torn meniscus (a partial meniscectomy) or perform a meniscus repair to place the edges of the meniscus together with sutures or tacks. Both are performed using a scope within the joint (arthroscopy). It is important to discuss these options with your family doctor and/or surgical specialist.
Knee locking is not a diagnosis; it is a symptom of a meniscus injury. Not everyone who experiences a meniscus tear will experience the locking of their knee joint. The type of meniscus tear and position of the tear will decide whether locking, clicking, popping or an inability to straighten the leg occurs (mechanical knee symptoms). I hope you found this blog both informative and educational.
Dr. Luciano Di Loreto, HBSc., D.C.