When I evaluate patients who feel that the kneecap is slipping, shifting, or suddenly moving out of place, one structure I pay close attention to is the medial patellofemoral ligament, usually called the MPFL. In simple terms, the MPFL is one of the main soft-tissue restraints that helps prevent the kneecap from moving too far toward the outer side of the knee.[1] In Bangladeshi patients, I often see this problem after a sports injury, a twisting fall, a stair-related accident, or a first episode of kneecap dislocation that was initially treated only with rest.
Many people hear the term MPFL only after an MRI report or an orthopaedic consultation. That can make the diagnosis feel confusing. I usually explain to my patients that the MPFL is important because it works like a stabilizing check-rein for the patella, especially in the early part of knee bending before the kneecap settles more securely into the femoral groove.[1][3] When this ligament is stretched, torn, or no longer functioning properly, patients may develop recurrent patellar instability, repeated fear of dislocation, pain around the front of the knee, and difficulty trusting the leg during walking, stairs, squatting, or sport.
What the MPFL actually does
The kneecap, or patella, should glide smoothly in a groove at the lower end of the thigh bone. The knee remains stable because of a combination of bone shape, muscle control, alignment, and soft-tissue restraints. The MPFL is one of the key medial restraints that helps keep the patella from slipping laterally, especially after the knee begins moving from full extension.[1][3]
One important point I want Bangladeshi patients to understand is that MPFL problems are usually not isolated in the broader sense of knee mechanics. A patient may have an MPFL tear after a first dislocation, but there may also be other contributing factors such as:
- a shallow trochlear groove
- maltracking of the patella
- generalized ligament laxity
- weakness of the quadriceps, especially the medial stabilizing component
- knock-knee alignment or rotational problems
- poor recovery after a first dislocation episode[1]
That is why a proper assessment matters. If we only treat pain and do not understand why the kneecap is unstable, the patient may continue to have recurrent symptoms.
Common symptoms of an MPFL injury or insufficiency
In my practice, patients with MPFL-related patellar instability usually describe one or more of the following:
- a history of the kneecap “popping out” or partially shifting
- sudden swelling after injury
- pain at the front or inner side of the knee
- fear when going downstairs or turning quickly
- a feeling that the knee is not trustworthy
- repeated instability during sports or daily movement
- difficulty sitting cross-legged, squatting, or praying comfortably
Sometimes the patient had one obvious dislocation event. At other times, the story is less dramatic, and they mainly complain of repeated giving way or apprehension. According to AAOS and MedlinePlus, patellar dislocation commonly occurs with twisting or a sudden change of direction and may lead to swelling, recurrent instability, and cartilage injury if the problem keeps returning.[1][2]
How MPFL problems happen
The most common mechanism is lateral patellar dislocation. When the kneecap moves out toward the outer side of the knee, the MPFL can tear or become stretched. In some patients, especially young active people, a first-time event may recover reasonably with bracing and rehabilitation. In others, instability keeps coming back because the ligament does not heal in a functionally stable way or because the knee has underlying alignment and tracking problems.[1][2]
In Dhaka and other parts of Bangladesh, I also see delayed treatment because many patients initially rely on home rest, pain medicine, massage, or unstructured exercise. That delay can sometimes allow quadriceps weakness, persistent apprehension, and abnormal tracking to become more established.
When I suspect more than a simple knee sprain
Not every front-knee pain problem is an MPFL injury. However, I become more concerned when the history includes:
- a visible kneecap dislocation
- immediate swelling after the injury
- repeated episodes of slipping
- pain combined with a strong fear response during patellar movement
- inability to return to sports or regular walking confidence
- locking, catching, or suspicion of cartilage injury
If the kneecap dislocates repeatedly, there is a greater risk of damage to the cartilage of the patella or the femoral side of the joint.[1][2] This matters because untreated instability is not only uncomfortable. Over time, it can contribute to further joint damage.
How I evaluate MPFL-related instability
When I evaluate patients with this problem, I begin with the story. I want to know whether the first episode was traumatic, whether the kneecap needed reduction, how much swelling developed, whether there were previous similar incidents, and how the patient functions now during stairs, prayer movements, squatting, work, and sport.
Physical examination
On examination, I assess:
- patellar tracking
- tenderness around the medial patellar structures
- apprehension during lateral patellar movement
- limb alignment
- quadriceps control
- generalized laxity
- associated ligament or meniscal findings
Imaging
X-rays are often important first tests. They help identify bony alignment issues, fracture fragments, and signs of patellar position abnormalities. MRI is especially helpful when I want to assess the MPFL itself, look for cartilage damage, loose bodies, bone bruising patterns, or associated soft-tissue injury.[1][2]
In selected cases, CT or more advanced alignment assessment may be useful if the patient appears to have significant maltracking or structural predisposition to recurrent dislocation.[1]
