Anterior Knee Pain
Pain at the front of the knee (anterior knee pain) is very common in sportsmen and women but also occurs in less active people. Up to 50% of football players and 25% of runners have been reported as having anterior knee pain to a significant level once per month or more.
The causes of pain at the front of the knee are numerous and include:
Causes of Pain
Causes of pain
Osgood-Schlatter’s disease – Adolescent condition causing pain at patella tendon insertion to tibia
Sinding-Larsen-Johansson – Tendinopathy at the lower pole of the patella before skeletal maturity
Idiopathic knee pain – Pain of unknown cause
Jumper’s knee – Tendinopathy at the lower pole of the patella after skeletal maturity
Quadriceps tendinopathy – Tendinopathy at the quadriceps tendon
Bipartite patella – Where the patella is made from 2 bone forming centres rather than one
Stress fracture – Normally transverse (across the patella) in athletes
Trauma-related lesions – e.g. Direct contact injuries causing structural knee damage
Chondromalacia – Slightly old-fashioned term implying softening of the patella cartilage
Osteochondritis Dissecans – A section of cartilage and bone may become loose behind the patella – likely injury related
Bone bruising – Either from a direct or indirect injury
Post-traumatic wear – Even when well treated pain following patella fracture is common
Syndromes and dysplasias – e.g. Nail patella syndrome, Down’s syndrome, Marfan’s syndrome
Maltracking – Common
Subluxation/tilt – Associated with muscle and softy tissue imbalance
Tumours – Rare
Fat pad impingment – an outsized infrapatellar fat pad caught in the knee on movement
Excessive lateral pressure – Caused by tight soft tissue on the outer part of the knee-cap
Complex Regional Pain Syndrome – An abnormal nerve response often to minimal trauma
Plicae – Catching of the inner folded lining of the knee often with associated cartilage injury
Bursae – Pain related to the bursa tissue around the knee
Patellar tendon mineralisation – Due to degeneration
Posterior cruciate ligament rupture – Psychogenic
Infrapatellar contracture – Often as a result of surgery, trauma or extended periods of immobility
Iatrogenic conditions – Problems resulting from a therapist’s intervention – such as painful scar following knee arthroscopy
As is clear from reviewing this list, the first stage in managing the problem is to establish a working diagnosis. This is done by the doctor, surgeon or physiotherapist listening to the patient and then examining them.
Often, tests will be arranged that help to clarify the diagnosis such as X-rays or scans. The story of the pain may be well localized to one area, but is usually vaguely anterior. It is often worsened by loading a bent knee (climbing stairs or inclines) or after sitting for prolonged periods and giving way episodes are often reported. Examination may reveal crepitus (grinding under the knee), catching, weakness and/or an effusion. The knee-cap may be tilted to one side or track abnormally on bending and straightening the knee.
The patella (or knee-cap) is a bone that sits at the front of the knee. It has a very important role in the function of the knee and, as can be seen from the list of causes of anterior knee pain, can often be involved in the cause of the symptoms.
The functions of the patella are as follows:
- It improves the efficiency of the quadriceps muscles (the bulky muscles on the front of the thigh) by lengthening the moment arm i.e. it makes the muscles that extend the knee able to create more force
- It decreases friction at the patellofemoral joint
- It improves stability of the knee
- It “centralizes” the quadriceps muscle pull – making the thigh muscles more effective
The knee-cap joint viewed from above at arthroscopy
Acute injuries to the patello-femoral joint include direct trauma, subluxation or dislocation, patellar fracture, quadriceps tendon or patellar ligament rupture. Many patients present with anterior knee pain with no injury.
80% of such patients respond to non-operative measures. Identify precipitating and aggravating activities. A physical programme includes quadriceps strengthening and in particular vastus medialis toning (straight leg raise with an externally rotated leg) with hamstring stretching. Patellar taping or S-Knee brace can help. If improvement is not seen within 6 to 8 weeks, the diagnosis might need to be reassessed and further investigations undertaken.
This often involves initial key-hole (arthroscopic) assessment of the knee when irregular cartilage can be trimmed back to stable and impinging tissue can be removed. It is also another “investigation” as it allows a thorough review of all the structures within the knee and allows the surgeon to view how the patella sits on the femur and how it moves up and down on bending and straightening. Many treatments for the above conditions can be carried out entirely with key-hole surgery or with “arthroscopic assistance”.