Knee Injury: The Lunge Lesion & Science

A 33-year old finance manager with severe knee pain and a knee injury that had already been examined by a surgical specialist. On the case notes, the surgeon had scribbled a differential diagnosis list. In the top was meniscal injury, and in the bottom were the words "lunge lesion." Science chiropractor, Dr. Alexander Jimenez investigates and discovers a little about this unusual injury.

"Lunge lesion" describes an isolated injury to the femoral trochlear groove -- a single surface of the patellofemoral joint. It was first described in 1978(1). Seen infrequently, it may happen in active young patients involved in recreational sports.

My client recalled a social game of badminton where he'd lunged forward quite deeply on to his right foot in an attempt to reach the shuttlecock for a net-shot. He described a deep ache in his knee and lack of ability to push back through his front foot to endure. He could not play on. During the upcoming few days that he developed swelling and pain, and detected "creaking in his knee when he flexed it. His symptoms hadn't resolved after two weeks of rest.

His examination revealed an effusion and tenderness along the medial joint line – hence the initial working diagnosis of a medial meniscal tear. Knee flexion into 60 levels was limited by pain and moderate palpable crepitus -- his knee ligaments seemed normal clinically. Examinations of his lumbar spine and hip joint were also regular.

Plain radiographs (x-ray) of the knee were ordinary and an MRI scan failed to identify any pathology. It confirmed that his ACL, PCL and collateral ligaments were all intact, and it showed up nothing indicative of meniscal tear. A small field of bone bruising was observable beneath the trochlea. The non-specific findings of this MRI further dampened my patient's mood.

His symptoms had been slow to improve, so the decision was made to proceed into a diagnostic arthroscopy, which, despite great improvements in MRI technology, remains the "gold standard investigation of intra-articular pathology from the knee. The arthroscopic findings were normal, except for one thing: an isolated split running lengthways across the femoral trochlear groove (see Figure 1, below). The under-surface of the patella was unaffected. The cartilage edges were stable and no loose flaps were identified which required debridement (tidying up). This reassured my client that he did really have an injury that explained his pain, and it provided information for us to invent a rehabilitation program for him.

The reason behind a lunge lesion injury is usually a rapid deceleration of the flexed knee using co-contraction of the quads and hamstrings(2), though other less common mechanisms like a direct blow to the patella are postulated. This injury classically takes place through a lunging motion of this type that happens in squash, tennis and netball(3). And, because functionally, it is the trochlea that acts to stabilize the patella between 30 and 100 degrees of flexion(4), loading of the joint in this way causes substantial shearing and compressive forces at the bottom of the groove. If the load is high enough, then a fissuring of the intercondylar cartilage can occur, resulting in painful crepitus (creaking) and catching when the knee is bent (envision the wedge shaped patellar- articulating surface dividing the cartilage of the groove).

Despite the injury to the trochlea froma a lunge lesion, the patellar surface remains uninjured. Various hypotheses have been proposed to explain why. One is that the articular cartilage of the patella is heavier and much more malleable than the cartilage of the trochlea. Another suggests that the encompassing soft-tissue supports of those highly mobile patella are somehow able to dissipate load better than the trochlea(5).

Treatment

A guessed lunge lesion doesn't always need arthroscopic debridement. Initial therapy should be the standard practice of rest, ice and elevation, progressing to mild passive and on to active knee mobility exercises. Passive mobilizations of the patellofemoral joint can be initiated after the acute phase (typically four to seven days post injury), as pain allows. Progression of practice back to running and cutting maneuvers will be decided by the customer's tolerance of these actions. Persistent or worsening swelling and pain without improvement within a few weeks would imply that further investigation and possible arthroscopic debridement is essential. The significant determinant of effective lunge functionality is volatile strength of the closed kinetic chain of the lower limb, but at the sports science laboratory, body mass, stamina and leg length has all been found to affect performance(6). So the "return to game" phase of rehabilitation must tackle all four factors. Strengthening the prime movers of the knee with functional activities and progressive loading should be the mainstay of therapy. This area of the program should include eccentric loading of the knee.

It's also very important to help the client regain correct motor patterns once the acute phase is over. An extensive evaluation of biomechanics may identify deficits or imbalances that could be adjusted with orthotics and/or construction techniques.

My patient progressed well and returned to his usual level of function. Unfortunately I am no longer connected with him, so it's not possible to create any longer-term evaluation of the natural history in this case. However, I would expect an injury to the load bearing surface of the patello femoral joint to heal slowly, with a higher likelihood of the individual developing patello femoral joint symptoms at some point in the future.

References
1. Cross MJ “The painful kneeÐ. Australian Patient Management: 11-21, August 1978.
2. Cross MJ, Morgan, DG. “The “Lunge” LesionÐ presented at The Third Congress of Knee and Orthopaedic Sports Medicine Section of WPOA, Sydney, 8-11 September 1993.
3. Cross MJ, Morgan-Jones RL “Knee syndromes and arthroscopic knee procedures. www.kneeclinic.com.au/papers/
ArthProcedures.htm (Access date: 9/12/2004).
4. Heegaard J, Leyvraz PF et al “Influence of soft structures on patellar three-dimensional trackingÐ. Clinical Orthopaedics and Related Research. 1994;299:235-243.
5. Morgan-Jones RL, Cross MJ, Morgan, DG “Isolated articular cartilage lesions of the femoral trochleaÐ. www.kneeclinic.com.au/papers/FemoralTrochleaLesions.html (Access date: 2/3/08).
6. Cronin J, McNair PJ, Marshall RN “Lunge performance and its determinantsÐ. Journal of Sports Sciences, 2003, 21, 49–57.