Knee pain is common among active teenagers and is often blamed on sports injuries or “growing pains.” However, persistent or unusual pain should be evaluated to rule out rare conditions like bone cancer.

Knee pain is a common complaint among active teenagers and is often attributed to sports injuries, overuse or growing pains. While most cases are harmless and improve with rest, persistent or unusual pain should not be overlooked. In some rare cases, ongoing knee pain can be linked to a more serious condition such as osteosarcoma, an aggressive form of bone cancer that primarily affects children and adolescents.

Osteosarcoma accounts for a significant proportion of bone cancer cases in young people, with around 75% of cases occurring before the age of 25. The condition commonly develops around the knee, making it particularly easy to mistake its early symptoms for a sports-related injury. This similarity can contribute to delays in diagnosis and treatment, highlighting the importance of recognising warning signs.

With a typical sports injury, pain should gradually improve with rest and medication. If it persists beyond one to two weeks, remains intense, or does not respond to painkillers, further investigation is needed.

Dr Tie Teck Liang, Consultant Orthopaedic Oncology Surgeon at Sunway Medical Centre, Sunway City, said parents and coaches should pay attention to the pattern and duration of a teenager’s pain. Typical sports injuries generally improve gradually with rest and medication, but pain that continues for more than one to two weeks, remains severe or fails to respond to painkillers may require further medical assessment.

Night pain can also be an important warning sign, particularly when it disrupts sleep or does not improve with medication. Other symptoms that warrant medical attention include persistent swelling, a noticeable lump, limping or pain that occurs without an obvious injury. Although these symptoms do not necessarily mean a child has cancer, they should be evaluated by a doctor when they persist or worsen.

Kids love to run, jump and trip, so knee pain from overuse and trauma is common. Early symptoms are often mild and mistaken for sports injuries, especially after a fall, creating a false sense of reassurance. 

One of the challenges in detecting osteosarcoma is that its early symptoms can resemble everyday injuries experienced by active children. A recent fall or sporting activity may initially appear to explain the pain, creating a false sense of reassurance. However, unlike a normal injury, a bone tumour can continue to grow and may eventually affect surrounding nerves and blood vessels, making treatment more complicated.

Early imaging plays an important role when persistent bone pain raises concern. An X-ray is commonly the first investigation and can reveal abnormal changes in the bone. If the findings appear suspicious, an MRI may be performed to determine the size and location of the tumour and its relationship with nearby nerves and blood vessels, while CT, bone scans or PET scans may be considered depending on the individual case.

When imaging suggests the presence of a bone tumour, a biopsy is required to confirm the diagnosis. However, the procedure needs to be carefully planned, as the biopsy site and tract may need to be removed during subsequent tumour surgery. Dr Tie emphasises that the biopsy should ideally be performed by the specialist surgeon who will carry out the definitive surgery. Poorly planned biopsies can affect surrounding tissues, complicate reconstruction and potentially increase the risk of recurrence.

Treatment for osteosarcoma has also advanced significantly over the years. While amputation was once commonly associated with the condition, modern treatment approaches allow limb-salvage surgery for selected patients. Surgery typically involves removing the tumour together with a margin of healthy tissue, followed by reconstruction using options such as endoprosthetic implants or biological reconstruction.

In selected cases, biological reconstruction using cryotherapy may be considered. This technique involves treating the patient’s tumour-bearing bone with liquid nitrogen at extremely low temperatures to destroy cancer cells before the bone is reimplanted. Using the patient’s own bone may offer certain advantages, including reducing size mismatch and supporting bone healing in appropriate cases. For growing children, preserving natural bone may also help address limb length differences and support long-term function.

Recovery extends beyond the operation itself, with rehabilitation playing an important role in helping young patients regain strength and movement. Physiotherapy may begin within days of surgery, while the overall treatment journey can extend for about a year when chemotherapy and surgery are combined, followed by long-term monitoring for recurrence or cancer spread. Emotional support is equally important, as clear communication and realistic expectations can help children and their families cope with the challenges of treatment.

Most teenage knee pain is not caused by cancer, but persistent, worsening or unusual symptoms should never be dismissed as growing pains. Parents, coaches and caregivers should pay attention when pain does not follow the expected recovery pattern, especially when it affects sleep or is accompanied by swelling, a lump or difficulty walking. Seeking medical evaluation early can help identify the underlying cause and, where necessary, allow treatment to begin sooner, potentially improving the chances of limb preservation, functional recovery and a return to an active future.