That was one of the main problems Pn Liyana noticed before she was diagnosed. What first seemed like stiffness around the knee continued despite painkillers and physiotherapy.

She had seen several doctors about the discomfort. At the time, the symptoms were thought to be related to the muscles around the knee. But the stiffness did not improve, and she still could not bend her knee properly.

Further investigations followed.

Pn Liyana underwent imaging and biopsies to find out what was causing the problem. The process was not straightforward. Her first biopsy did not confirm cancer, and a second biopsy was also inconclusive.

As Dr Choong Chee Leong explained:

The first biopsy suggested myositis ossificans, while the second showed inflammatory tissue behind the knee. Despite this, the findings on her scans remained concerning.

Pn Liyana’s case was reviewed by a multidisciplinary team. The radiological findings raised strong suspicion of parosteal osteosarcoma, a rare, low-grade type of osteosarcoma that develops on the surface of the bone.

According to Dr Choong:

Parosteal osteosarcoma accounts for only a small proportion of osteosarcoma cases. It is commonly found around the distal femur, the lower end of the thigh bone close to the knee.

In Pn Liyana’s case, the tumour was located at the back of the knee.

Dr Choong also noted how uncommon the condition is in his own practice.

One surgical option would have involved removing the affected part of the distal femur and replacing it with an implant.

But after reviewing Pn Liyana’s scans, Dr Choong saw that there appeared to be a space between the tumour and the knee joint.

That opened up another possibility.

Dr Choong proposed computer navigation-assisted surgery to help guide the removal of the tumour while preserving the natural knee joint.

As he explained:

For Pn Liyana, preserving the knee was particularly important because the stiffness had already affected her ability to bend it fully.

The aim was to give her the best possible chance of returning to normal movements after treatment, including walking, squatting and the positions needed for daily prayers.

Dr Choong explained the treatment options and the reasoning behind the proposed procedure before Pn Liyana agreed to proceed.

The decision to preserve the natural knee was also made with the longer term in mind.

Using an implant can be necessary in some cases, but implants may carry risks over time, including loosening, infection or implant failure.

Where possible and appropriate, preserving the patient’s own joint may avoid some of these issues.

For Pn Liyana, the treatment plan was therefore not only about removing the tumour. It was also about keeping as much normal knee function as possible.

After her treatment, she spoke simply about her experience with Dr Choong and the people who cared for her:

Pn Liyana’s story also shows why persistent bone or joint symptoms should be checked, especially when they do not improve as expected.

Most knee pain and stiffness are not caused by cancer. But unusual or persistent symptoms may need further investigation.

Dr Choong advises people with ongoing bone pain to seek medical assessment rather than assuming that the discomfort is only caused by muscle strain or overuse.

An X-ray can often be the first step. If the cause remains unclear, further imaging such as an MRI may be considered.

For Pn Liyana, the journey began with a knee that simply would not bend properly.

The initial tests did not immediately provide an answer. It took further investigation, repeated review and multidisciplinary discussion before the team could decide on the next step.

She was eventually treated for a rare parosteal osteosarcoma near her knee, with surgery planned around two priorities: removing the tumour and preserving her natural knee joint.

Her experience is also a reminder that when a symptom continues despite treatment, it is worth finding out why.