Osgoode Schlatter Disease: Why does my child’s knee hurt?
Osgoode Schlatter Disease (OSD) is a common repetitive injury of the knee that occurs in adolescent boys (aged 12 to 14) and girls (aged 10 to 13) around the time puberty hits. It is characterized by a pain in the lower part of the knee (below the kneecap) that gets worse with activity and better with rest. Before we dive into the details, let’s do a quick anatomy lesson.
The knee joint is made up of 3 bones interacting with one another: the femur (or thigh bone), the tibia (or shin bone), and the patella (or knee cap). These bones are connected through ligaments, muscles and tendons. Ligaments connect one bone to another while tendons (that are an extension of a muscle) attach the muscle to the bone.
The front part of the thigh contains 4 muscles that are collectively referred to as the Quadricep Muscles or the Quads. These muscle begin at the pelvis bone and the top part of the thigh bone and travel down the thigh into the knee cap and the shin bone through the Quadriceps tendon. But that’s not all- the quadriceps tendon inserts into the front of the knee cap while the patellar tendon extends from the knee cap into the top of the shin bone.
The Quads are important as the help with extending (motion of kicking) our knees and helping our knee cap travel (or track as we call it) within the knee joint. This means that any activities that require both extending our knee or controlling the rate that we bend our knees require the Quads. This can include jumping, kicking a ball, squatting, running, using stairs, or even cycling.
Now that we have considered the muscles and tendons, let’s look at the bones. Both the tibia and the femur have growth zones- these are areas typically located at either end of a bone that allow for the bone to grow and lengthen. These areas are referred to as apophysis and are more cartilaginous or soft than the rest of the bone.
So what is actually going on?
During puberty, the bones begin to grow at a faster rate than the muscles and the tendons. This means that the quadriceps muscle that starts on the pelvis and thigh bones can become stretched as the thigh bone (femur) and the shin bone (tibia) grow and elongate. What happens to a muscle that begins to be pulled apart? It begins to stretch and essentially becomes tight.
This tight quadriceps muscle then starts to pull on the knee cap (where it inserts) upwards. This means that the patellar tendon that extends from the knee cap to the shin bone gets tighter as it gets pulled on. Why is this an issue? The patellar tendon can begin to pull on where it inserts into the shin bone just below the knee cap which can start to cause some pain since this is located on a growth zone.
So why the pain? When the lengthened Quad muscles are constantly and repeatedly used in activities (sports or otherwise), it can cause the pulling at the shin bone to become too much for the bone. This can lead to an inflamed shin bone exactly where the patellar tendon inserts into it. This problem is heightened by the fact that this insertion on the tibia is on a growth plate and therefore the bone is more soft than typical bone once it is done growing. In summary: the constant concentrated force of the Quad muscles on the shin bone (through the patellar tendon that inserts on a growth zone) begin to cause pain.
This can still be classified as an overuse injury with the slight difference that it occurs on a softer growth zone. So at first, the Quads pulling did not cause pain, but after repeatedly pulling on the same spot, the bone area became tender, the patellar tendon was starting to wear down and required time to heal that it was not getting. This constant use eventually started to cause pain which you feel now. If this constant pulling pressure on the shin bone continues, the bone can actually break at the exact place of the patellar tendon (known as an avulsion) which can make the problem worse. An avulsion can either be micro (where it happens at a cellular level- still painful especially when there are multiple) or macro- where the tendon has clearly pulled of a bone fragment (can be seen on x-rays). In the process of trying to heal this, there can end up being a large bony prominence at the location where the patellar tendon is pulling on the shin bone.
The main symptom is PAIN at the exact location that the patellar tendon meets the shin bone (right underneath the kneecap). When this area is pressed down on, there can be an increase in pain and tenderness due to swelling. Certain activities also reproduce the pain in this exact location, such as running, jumping, or kicking a ball, because they require the use of the Quads.
Resting or taking time off of sports helps reduce the pain because the Quads are not pulling as much on the shin bone. However, once returning to activity too soon, the pain usually comes back.
In some cases, you can feel if where the insertion of the patellar tendon on the shin bone has grown (due to bone growth as a healing mechanism). This is typically tender as well.
As well, any stretching of the Quads muscles – including testing during an assessment- will cause pain at the same location because the patellar tendon continues to get pulled, however this time it is due to the tightness of the Quads (and not the strength of the Quads repetitively pulling).
Treatment: What do we do about it?
Treatment starts with first treating the pain and the swelling that has occurred and promote healing to occur. This involves RICE- Resting, Icing, Compression, and Elevation. In addition to Ice, modalities such as Ultra Sound and IFC can be used to help reduce the swelling and help with pain management. In addition to this, active assisted range of motion can help with the swelling, pain, and maintaining some strength while on rest. In addition, the use of non-steroidal anti-inflammatory medications can help with the swelling and pain as well.
There is some debate however with respect what resting actually means. Some protocols say that there should be a complete cease of activities (including sports) that further cause pain in the shin bone. Other protocols say that limiting or modifying activities is enough to allow for the tendon to heal while allowing pain to be the guide. The severity of the case, and clinical expertise of a physiotherapist, would provide enough information to determine which approach would be best. The main purpose is to allow your body the time to heal without causing further injury.
At the appropriate time, following the initial healing stage, a physiotherapist will gradually start to load muscles and tendons to help bring back strength in the leg (which can be affected while on rest). This will begin with low-intensity strength training for muscles in the legs to help offload the patellar tendon. This program will be designed per person and is customized by the physiotherapist. It will involve strengthening the muscles around the leg to help offload the knee joint and beginning light isometric strengthening at the knee joint. The program will eventually progress to eccentric strengthening which has been shown to be an effective way to begin loading tendons. Higher intensity muscle strengthening begins at later stages once the tendon has been given time to heal.
The therapist will also include stretching into the program to allow for lengthening of muscles. At first, the Quads will not be stretched to avoid further pulling on the patellar tendon and the shin bone. Stretching can be incorporated into Active Range of Motion exercises. Typically, stretching will begin in the hamstrings which helps offload the Quads.
How long will this last?
Because O.S.D. occurs in adolescents due to the growth plate being affected, typically a case of O.S.D. can last up to 2 years or until the child has passed the growth spurt. This does not mean pain constantly for 2 years or rather flare-ups with increased activity. However, with a proper program of RICE, stretching, and strengthening, a flare-up can be prevented to a degree and treated as necessary. In some cases, the pain does not return.
If symptoms continue after conservative treatment, further examination will need to be done. This may reveal loose bone fragments in the area that would require surgery. In this case, the child would have to stop activity and prevent further injury since the surgery must be performed after the child has grown. This is to prevent affected the growth zone, because interfering can cause the zone to stop growing earlier than it normally would.
If the symptoms continue without any conservative treatment, this can lead to future complications. If the bone has not avulsed yet, there is an increased risk that it may with continued painful activity. With a decrease in effective healing and continued use, the child can have increased risk of patellar tendinopathy in the future.
What do I do if I feel I, or my child, has this?
The first thing would be to visit a physiotherapist so you can get assessed fully. There are many other knee conditions that could be at play and so it is best that a professional diagnose the condition. Following the treatment, the physiotherapist will be able to determine what the best course of treatment will be for your specific case.