Huw David

Knee Cap Injuries

Knee cap problems are very common. Thankfully, the majority of patients Huw David sees with knee cap injuries do not require orthopaedic surgery.

The knee cap or patella lies within a shallow groove or sulcus overlying the lower end of the thigh bone (femur). It is the link in the attachment of the powerful thigh muscles ("Quads") is to the upper tibia or shinbone via the patella tendon. The patella normally moves up and down within the groove during knee flexion and extension. The under-surface of the patella is covered with articular cartilage that allows for smooth movements. This is just as well for huge forces pass across the patellofemoral joint (PFJ) during normal day-to-day activities. Up to 3.5 times body weight passes across the PFJ when walking down steps and up to 7 times bodyweight when squatting.

Problems within the PFJ are generally the result of inflammation or wear of the surfaces or abnormal movement (tracking) of the patella. Often referred to as anterior knee pain or chondromalacia patellae it frequently occurs in teenagers and young adults and is characterised by pain within the front of the knee made worse by walking up or down steps or on inclines. Crepitus ('creaking") within the PFJ is common, but there is often surprisingly little correlation between the amount of crepitus and pain. Instability of the PFJ is also most frequently seen in the younger age group. Symptoms may range from nothing more than a feeling of instability or discomfort to recurrent dislocations of the patella.

With each condition it is important on physical assessment to exclude causes of mal alignment or instability of the patella. Muscle weakness or unbalanced thigh muscle activity often coupled with excessively taught supporting structures are common findings. The mainstay of treatment involves advice on aggravating or precipitating activities and appropriate physiotherapy. Surgery is uncommon.

Arthritis of the PFJ may develop as part of degenerative change within the knee in general, but is also seen in isolation in approximately 5%. Treatment varies from the use of painkillers and physiotherapy, injections and replacement surgery of the patellofemoral or complete knee joint.