What Causes Knee Pain When Bending
The knee is one of the largest and more complex joints of the human body. There are four bones that account for this articulation. We have the femur (thigh bone), patella (kneecap), and both the tibia and fibula (shin bones). Movement at the knee joint primarily occurs in a forward to backwards manner (flexion and extension), and this can be appreciated when we run, kick a soccer ball, or go up and down the stairs. There are smaller accessory movements that also occur at the knee as well, but how much is usually controlled by many strong ligaments surrounding the knee joint.
The knee is one of the most important weight-bearing joints, and it is fundamentally involved in most of the activities we carry out during our day. Our weight-bearing joints are built to withstand large physical forces that are transferred between our body and the ground during activities such as jumping or running, and the knee is no exception here. The body’s demands on the knee make it susceptible to a variety of painful conditions ranging from direct trauma, repetitive strain injuries, to arthritis from long-term wear and tear. Pain or injury to this joint can therefore be highly disruptive to our quality of life. Understanding where your pain is coming from or why you may have pain in your knee is important, and this article will aim to guide and educate you as to what may be going on with your knee, the causes of knee pain, and whether you should be seeking treatment.
Sprain or Strain Injuries
Ligaments around the body provide stiffness and support to the joints of our body, allowing them to move freely, but limiting movement that would potentially threaten the safety and health of the joint. Our ligaments form a passive support system and help keep our joints in place. If there is enough damage to an important ligament of a joint, the stability and overall joint can become compromised. Likewise, the knee is supported by several important muscles and their tendons. While some muscles are acting to move the joint, others are acting to support the knee and keep it in place. Injuries to ligaments are referred to as “sprain injuries”, and injuries to muscles or their tendons are referred to as “strain injuries”. Both of these types of injuries can cause knee pain.
Strain injuries are very common. When you overstretch or forcefully contract a muscle and its tendon you may be left with an injury. These injuries are generally graded 1-3. A grade 1 injury represents microscopic injury to the fibres of the muscle and may result in soreness and difficulty using the muscle due to pain. A grade 2 injury represents more significant tissue injury and partial tearing of the muscle or tendon. These injuries result in a higher degree of pain and disability and sometimes swelling and bruising. A grade 3 injury represents a full tear and loss of integrity to the affected muscle. The function of the affected muscle or tendon is completely compromised, and there can be significant swelling or bruising. A grade 3 injury is often treated surgically. Within this grading system, it should also be understood that strain injuries to tendons often take longer to heal than similarly graded injuries to muscles. Tendons do not benefit from the same blood supply as muscles and do not have the same healing potential. Therefore, tendon strains can often wax and wane and if not treated properly, can become chronic.
“Runner’s knee” or “jumpers’ knee” are examples of common strain injuries to the knee. These are vague terms often used to describe injury or irritation to several different types of tissues around the front of the knee, including the patellar tendon, quadriceps tendon and iliotibial band. The tendons around the knee will help with the absorption of forces through the knee during activities like running or jumping. With overuse, repetitive loading, or overload, injury can occur to these soft tissues and result in pain around the front of the knee.
Like strain injuries, ligament sprains also utilize a grading system based off the severity of the injury, ranging from grade 1 (microscopic tearing) to grade 3 (full rupture of the ligament in question). There are four major ligaments around the knee that can be injured in isolation or combination. Two reside on the sides of the knees (MCL on the inside and LCL on the outside). These inner and outer ligaments prevent excessive side-to-side movements of the bones of the knee. The other two are located deep within the knee joint (ACL and PCL) and prevent unwanted twisting and forwards/backwards sliding of the bones of the knee. The anterior cruciate ligament (ACL) is the most important ligament in the knee as it keeps your joint stable through all the weight-bearing activities we do. It can be injured from landing with a hyperextended knee, planting and twisting through your leg forcefully, or from being hit in the knee during contact in sports. If this knee is injured badly (grade 2-3), it is often treated surgically. The remaining ligaments are not often treated surgically unless they are injured severely (grade 3). More often than not, all these injuries (regardless of whether surgery is required) are treated successfully with manual therapy and the appropriate exercise rehabilitation therapy.
A meniscus is a small cartilage structure in the knee that partly divides the joint between the adjacent bones. We have an inner (medial) and outer (lateral) meniscus in each knee. They help to provide stability to the knee when bearing weight, and they help disperse friction in the joint by spreading the load of the body’s weight over a greater surface area. The menisci can be injured acutely through a traumatic injury, such as hyperextending the knee or twisting the knee forcefully, or they can be subject to wear and tear over a long time. A meniscus tear can be the reason your knee hurts when climbing stairs. The meniscus does not have a very great blood supply and is not innervated well by the nerves around the knee. Therefore, it is not uncommon to have an injury to this structure and not know. Many people will show signs of injury or wear and tear on MRI despite no history of pain. However, in some cases, a meniscus injury can lead to a warm and swollen knee when the joint capsule becomes inflamed. Meniscus injuries are always treated conservatively through manual therapy and exercise rehabilitation. In some cases where they do not respond to conservative efforts, surgery is offered. However, this is not as common practice as it has been in the past and is usually reserved for persistent painfully swollen knees that interfere with quality of life and have not responded to a trial of therapy.
Osteoarthritis (OA) can affect most of the joints of the human body, but we are especially susceptible to acquiring it in weight-bearing joints such as our knees. Years of supporting our body weight and day in and day out stress on these joints can accelerate wear and tear when compared to a joint like the elbow. It most commonly affects those over the age of 50. The knee has three distinct compartments which can develop arthritis. There is an inner (medial) and outer (lateral) compartment between our femur (thigh bone) and tibia (shin bone). There is a third compartment beneath our patella (kneecap) and the underlying knee joint. This space is often referred to as the patellofemoral compartment and when there is thinning of the cartilage here, the term chondromalacia patella is often used. In osteoarthritis, the cartilage surfaces of the joint begin to wear down over time, resulting in less shock absorption, a reduction in synovial fluid inside the knee, extra bone growth around the knee, degeneration in other tissues such as the menisci, and altered movement of the joint.
Knee osteoarthritis is graded in terms of severity and the number of compartments affected. With mild to moderate knee arthritis, conservative management, including weight loss, exercise, and nutritional changes is always the first-line approach. Movement is the best medicine for these knees. If osteoarthritis becomes severe, and there is significant change to the structure and function of the joint, accompanied by pain and interruption of quality of life, then more invasive treatment is often needed. Medications can be used to help manage symptoms of osteoarthritis. Injections of substances such as cortisone, hyaluronic acid and protein-rich platelets are also often recommended for an end-stage knee. When there are no other options, joint replacement surgery is sometimes necessary. In all stages of the disease, exercise is the scientifically recommended treatment of choice.
A popliteal cyst (also known as a Baker’s cyst) occurs when there is too much synovial fluid inside of the knee joint due to inflammation, This fluid will form a cyst and outpouching of the joint capsule and can sometimes be felt deep within the back of the knee. A cyst that is large enough can press on other tissues and become compressed when we bend our knee, resulting in pain in the back of the knee. These cysts often occur from inflammation associated with various types of arthritis, or alongside damage to the cartilage of the joints of the knee. Once the swelling comes down, the pain usually follows. In cases where the swelling is not treated, these cysts can occasionally rupture, resulting in sharp pain in the knee and calf muscle, as well as a sensation of warm water running down the inside of the leg.
Referred Pain to the Knee
There are several conditions in which a person can develop knee pain, despite any pathology being present in the knee whatsoever. The lower back and hip joint are both known to refer pain as far as the knee and even beyond when problems arise. Conditions of the spine where the discs or joints become compromised, potentially leading to a pinched nerve, can result in pain down the leg. If the L3-4 and L4-5 spinal levels are affected, you may experience pain that refers to the knee. If you develop an onset of pain that seems to travel to the knee and is accompanied by a new onset or change in your back pain, it may be suitable for you to be seen by a health professional who can help determine whether your pain is knee related or coming from your lower back.
There are several muscles around the hip joint that are known to refer pain down to the knee. When a muscle becomes tight and irritated, pain can often be felt beyond the borders of that muscle, and in the case of some of the muscles on the front or side of the hip, we will often feel the pain spread down as far as the knee. Many cases of knee pain are blamed on the iliotibial band (IT band), however, often, the problem is higher up in the hip. There should always be an assessment of the hip whenever there is knee pain.
Why do my knees crack and pop when I bend them?
The term “crepitus” is used to describe the rubbing, clicking or popping sensations that we feel in or around our joints. It may occur in tandem with a joint disorder or completely on its own. Crepitus can occur when the roughened surfaces of two bones rub together, causing the physical grating of cartilage and/or bone. While this sensation is not normally or commonly painful, it can be quite alarming or concerning to patients. If crepitus is painful, it is usually related to joint damage and/or compression of tissues between the reduced joint spaces. There may also be observable swelling, redness, reduced joint movement or malformation.
Crepitus can also occur when tissues around the knee become inflamed. Many of the highly movable joints in our body have one or more bursa (a fluid-filled sac which aims to reduce friction or compression of tissues against one another). The bursa can become inflamed due to trauma, repetitive use injury, or other disorders, resulting in “bursitis.” With increased fluid inside the joint, the inflamed surfaces can rub together and create the sensation of crepitus. In the knee, there are several bursae around the kneecap and hamstring tendons in the back of the knee.
When crepitus is found under the front of the knee, it is commonly the result of abnormal gliding of the patella (kneecap). Tight muscles can pull and cause abnormal gliding or tracking of the kneecap in its groove. This may or may not be painful. We often term this “patellofemoral syndrome.” If there is also a breakdown of the cartilage underneath the kneecap, then this can be referred to as “chondromalacia patella”.
Other joint sounds include joint cavitation and tendon rubbing or snapping. When you pop your knuckles, you will hear a pop. Many people will hear this when they bend down into a squat in their knees. They will hear a single loud pop! The sound you are hearing is the release of several gas bubbles from a pressurized joint. Think of what happens when you open a can of pop. Once these bubbles are released, the joint pressure is reduced, which is why you cannot repeatedly “crack” or pop your joints.
Why do my knees hurt when I bend them, or go up and down stairs?
Many knee pain patients will report that they have trouble with deep bending through the knee, or going up and down stairs due to an increase in anterior knee pain. When you bend the knee under load, such as when you go down or up the stairs, there are a lot of muscles that are working, and putting pressure on the kneecap via their strong tendinous attachments. The patella (kneecap) sits above a groove in the femur (thigh bone) when we are standing. When we start to bend the knee, the kneecap glides into this groove. This groove keeps the kneecap stable and in place. Within the groove, there will be building pressure within the patellofemoral space (space between the kneecap and other bones of the knee). Under normal circumstances, we will be able to tolerate this increase in joint pressure without any concerns. However, when there is thinning of the cartilage on the underside of the kneecap, as is the case of “chondromalacia patella”, our tolerance for compression is lessened, and this may provoke feelings of pain. Further, if there is osteoarthritis in the knee, affecting the joint space or shape of the bone, this can slightly change the way the kneecap tracks and alter the forces seen acting on the knee.
How Can Manual Therapy Help You Recover From Knee Pain?
At The Pain & Wellness Centre, we see patients with both new and chronic knee pain. Following a comprehensive assessment of your pain, our Chiropractors will work with you to develop a plan of management that is personalized. They will often use a combination of both passive and active therapeutic approaches to help you with your pain. Your treatment will not only be directed at the knee only, but also the neighbouring areas of your body that play a role in supporting the knee, such as the ankle, hip and lower back. Many knee pain conditions are complicated or driven by non-painful muscular imbalances or problems at other areas in the body, and if you are not looking at the whole person and how their knee is a component towards the movement of the whole body, you may struggle to resolve the knee pain.
For passive therapeutic interventions, our therapists are trained in applying various active soft tissue therapies, medical acupuncture, as well as offering specific modalities such as shockwave therapy or interferential current as needed. They will use some of these tools and techniques to help reduce your pain and/or improve the way your knee, hip or ankle moves.
The most important part of your therapy is the active therapeutic interventions that your Chiropractor will teach and review with you. Exercise is the most appropriate and important part of therapy for any knee injury, whether it’s new or old! They will teach you exercises that will help improve endurance and build physical capacity in the muscles, tendons and other soft tissues of your knee and surrounding areas. The goal with exercise is to make you more resilient and allow for you to be more active and tolerate more physical strain without pain stopping you!