Anterior Knee Pain (AKP)
the patella (kneecap), patellar tendinitis, quadriceps tendinitis or impingement of the synovial plica (the lining in the joint capsule). When large force is put on the knee joint, especially in deceleration with a heel strike (when walking down a hill or down stairs), the tendon of the quadriceps contract causing resultant forces over the knee joint's cartilage. Eventually, the cartilage will start to break down and become fragmented, causing anterior knee pain.
It is more prevalent in females and begins to develop during the early twenties. Anterior knee pain is characterised by pain when bending the knees, climbing stairs, running or jumping, or when playing sport. In severe cases, the knee can even start to swell. Anterior knee pain is a very common condition affecting both knees of high-performance athletes as well as more inactive low demand patients.
Treatment options for anterior knee pain
There are several different conservative options for treatment of anterior knee pain which may include physical adjustments like a change of sports or training and strengthening of the quadriceps and core muscles to reduce overload on the knee joint cartilage.
Surgical treatment options for anterior knee pain
In cases where there is severe fragmentation of the knee joint cartilage and considerable anterior knee pain, arthroscopic knee surgery may be done to smooth and remove fragments in the kneecap. This surgery must, however, be combined with a dedicated exercise program to ensure the best outcome. Surgical readjustment and realignment of the kneecap can also provide good results in patients with anterior knee pain caused by abnormal tracking or abnormal positioning of the kneecap. In patients where there is an ‘overhang' of the kneecap, removal of that extra bone can lead to an improvement in symptoms. In more severe cases, a total or partial knee replacement may only be suitable for specific patients due to the limitations post-surgery.
Basic biomechanics
The kneecap (patella) sits over the front of the knee joint. As the knee flex from extension (bend or straighten), the underside of the patella glides into its groove (trochlea) in between the 2 condyles of the femur (thigh bone)
It has a relatively short excursion in the trochlea, but high forces are generated, especially in deceleration with heel strike. This is when the quadriceps (thigh muscle) tendon eccentrically contracts causing resultant forces over the kneecap joint cartilage.
When the forces exceed the critical load of kneecap cartilage it will start to cause breakdown collagen matrix and fragmentation the knee will start to hurt even before permanent cartilage damage occur.
Causes for cartilage overload
The kneecap in an abnormal position (too high or not central) (abnormal tracking of kneecap) Weakness of the muscles on the front and back of your thigh especially controlling deceleration as in walking down hill or down stairs Weak hip or trunk control leads to increase loads at kneecap joint
Conservative treatment options
Decrease the load on the kneecap joint by adjusting activities (change sport if possible) Core muscle training program Training program to strengthen Quadriceps muscle, focussing on eccentric training.
Surgical treatment options
Smoothing of the kneecap cartilage in cases where there is severe fragmentation with arthroscopic instruments, can bring improvement of symptoms in certain cases. But this procedure must be combined with a dedicated exercise program.
Adjustment of kneecap alignment by repositioning can deliver good results in patients with abnormal tracking or positioning of the kneecap.
In patients where overhang (lateral facet osteophyte) of the kneecap have developed, removal of that extra bone can lead to improvement in symptoms.
Kneecap replacements should be reserved for very specific indications due to the lack of favourable results of long term survival.