The only time feeling weak at the knees would be a normal phenomenon is when you are standing at the edge of a cliff or doing a bungee jump.
Experiencing weak knees with joint pain can be quite debilitating. We can sit, stand, walk, run and move about easily because of our knees. What we should know is that our kneecap is a part of the knee joint and it should remain ‘in the groove’ for optimal function.
The kneecap, also called the patella bone, is a sesamoid bone in the front of your knee. It’s called the sesamoid bone as it has the shape of a sesame seed. The sesamoid bone is a bone that grows within a tendon. The patella has many biomechanical functions which are responsible for the protection, support and movements at your knees.
Anatomy of the knee cap
The knee joint (Patellofemoral joint) is comprised of the three bones. The thigh bone (Femur), the shin Bone (Tibia) and the patella (Kneecap). The patella lies in a groove at the lower end of the femur and acts as an attachment point for the four main muscles of the thigh (quadriceps). The lowest part of the patella continues on as a tendon that attaches to the tibia. The muscles pull on the patella and the patella pulls on the tibia allowing you to straighten your knee from a bent position.
Cartilage of Patella
The cartilage is a taut protective structure underneath the kneecap. It found to be among the thickest cartilage in the body providing cushioning for the patella bone. The cartilage helps to prevent friction and acts as a shock absorber protecting the bony surfaces.
Why is the patella so important?
- Patella functions as a natural pulley
The kneecap plays an important role, it increases the leverage of the quadriceps tendon (thigh muscle tendon) and protects the front of the knee from direct trauma.
The quadriceps muscle is providing the force like the man in the picture, the patella bone acts as a fulcrum to provide more leverage for lifting the stone.
In real life though, the patella is a little more complicated by not only providing increased force, but also by aiding in balancing forces as well as providing a direction for the forces.
- Prevents excessive weight-bearing compressive stress
As weight bearing stress falls on our knees, the patella acts as a spacer protecting the quadriceps tendon and bone from coming into compression and creating a frictional force. The patella also allows for smoother movements when bending and straightening the leg.
- Maintaining the Quadriceps Angle
The quadriceps angle or the Q angle is determined by drawing one line from the hip bone (anterior superior iliac spine) through the center of the patella and a second line from the center of the patella through the leg bone (tibial tuberosity).
As the Q angle increases above 15 degrees, it potentially could cause the patella bone to move out of its groove. This is as if the Q angle is increased, forceful contraction of the quadriceps muscle can cause the patella to move outwards and possibly dislocate. Slight changes in the Q angle would cause imbalances in the muscle forces causing compression stress, symptoms of pain and inflammation at the knee joint.
Knee Pain related to the Patella
Although patellar dislocation, fracture, and patellar tendon inflammation are the common sports-related injury. Many patella related problems may also occur during daily activities.
- Runner’s knee/ Patellofemoral pain syndrome
Patellofemoral joint pain is a condition seen in runners causing pain during running or while at rest. Pain usually occurs in the front of the knee.
- Condromalacia Patellae (“soft cartilage under the knee cap”)
This often affects young, otherwise healthy athletes. Chondromalacia patella is one of the conditions that cause pain in front of the knee. When pain exists in the absence of cartilage softening, it can be referred to as patellofemoral pain syndrome (Runner’s knee). Although it’s common to sporting individuals, it can also affect individuals with weak quadriceps muscles. It is common among individuals engaging in activities like football, cycling, tennis, weightlifting, runners. In other words, any sport that involves running, jumping, squatting and landing on the knees.
- Prepatellar bursitis (between patella bone and skin)
Prepatellar bursitis has historically been referred to as “housemaid’s knee”, which is derived from a condition that was commonly associated with individuals whose work necessitated kneeling for extended periods of time. Prepatellar bursitis is common in professions such as carpet layers, gardeners, roofers, and plumbers.
- Infrapatellar Bursitis (Below the Kneecap)
This is common among individuals who engage in activities that involve kneeling down for long hours causing inflammation of the bursa below the patellar tendon. It can also occur conjunctively with a condition called jumper’s knee.
- Suprapatellar Bursitis (Above the kneecap)
Injuries such as direct trauma and overuse injury to the bursa beneath the quadriceps tendon cause inflammation of this bursa.Overuse injuries caused due to running on uneven surfaces or doing jobs that require crawling on the knees.
Patellofemoral arthritis occurs when the articular cartilage on the underside of the patella wears down causing friction between the patella and the end of the thigh bones. It gets extremely painful during weight bearing with swelling, inflammation around the knee. It is generally a degeneration condition which requires immediate medical attention to manage the condition.
- Patellar Dislocation
This type of injury happens when the kneecap (patella) moves out of its groove due to the sudden change in direction engaging in high impact sports. It most commonly occurs among young girls or hypermobile individuals due to laxity and increased hip angle. Direct trauma to the kneecap could also cause dislocations.
As a precautionary measure, using knee pads during sports and regular exercises of your knee muscles will have great benefits for your patella. Generally, most of the injury conditions can be managed with appropriate treatment and rehabilitation.
However, if you’ve only begun to feel pain while doing activities or just by standing, you might like to seek medical attention to prevent long-term pain or further damage to your patella.